diff --git a/aidial_adapter_vertexai/chat/attachment_processor.py b/aidial_adapter_vertexai/chat/attachment_processor.py
index 57a5ef8..f60a560 100644
--- a/aidial_adapter_vertexai/chat/attachment_processor.py
+++ b/aidial_adapter_vertexai/chat/attachment_processor.py
@@ -27,7 +27,7 @@
 from aidial_adapter_vertexai.chat.conversation.factory import (
     ConversationFactoryBase,
 )
-from aidial_adapter_vertexai.chat.errors import ValidationError
+from aidial_adapter_vertexai.chat.errors import UserError
 from aidial_adapter_vertexai.chat.gemini.conversation_factory import PartT
 from aidial_adapter_vertexai.dial_api.request import get_attachments
 from aidial_adapter_vertexai.dial_api.resource import (
@@ -92,11 +92,18 @@ async def process(
 
         except Exception as e:
             log.error(
-                f"Failed to download {dial_resource.entity_name}: {str(e)}"
+                f"Failed to process {dial_resource.entity_name}: {str(e)}"
             )
             if isinstance(e, ResourceValidationError):
+                # Errors specific to a particular resource
                 return e.message
-            return f"Failed to download {dial_resource.entity_name}"
+            elif isinstance(e, UserError):
+                # Errors not specific to any particular resource
+                # typically raised by validators
+                raise e
+            else:
+                # Unexpected runtime exceptions
+                return f"Failed to process {dial_resource.entity_name}"
 
 
 @dataclass(order=True, frozen=True)
@@ -153,7 +160,7 @@ async def process_resource(
         self, dial_resource: DialResource
     ) -> Resource | None:
         if not self.processors:
-            raise ValidationError("The attachments aren't supported")
+            raise UserError("The attachments aren't supported")
 
         for processor in self.processors:
             resource = await processor.process(self.file_storage, dial_resource)
@@ -218,36 +225,47 @@ class AttachmentProcessorsGenAI(AttachmentProcessorsBase[GenAIPart]):
     pass
 
 
-def max_count_validator(limit: int) -> InitValidator:
+def max_count_validator(category: str, limit: int) -> InitValidator:
     count = 0
 
     async def validator():
         nonlocal count
         count += 1
         if count > limit:
-            raise ValidationError(
-                f"The number of files exceeds the limit ({limit})"
+            raise UserError(
+                f"The number of {category} files exceeds the limit ({limit})"
             )
 
     return validator
 
 
-def max_pdf_page_count_validator(limit: int) -> PostValidator:
-    count = 0
+def max_pdf_page_count_validator(
+    limit_per_request: int | None,
+    limit_per_document: int | None,
+) -> PostValidator:
+    total_pages = 0
 
     async def validator(resource: Resource):
-        nonlocal count
+        if limit_per_document is None and limit_per_request is None:
+            return
+
+        nonlocal total_pages
         try:
             pages = await get_pdf_page_count(resource.data)
             log.debug(f"PDF page count: {pages}")
-            count += pages
+            total_pages += pages
         except Exception:
             log.exception("Failed to get PDF page count")
-            raise ValidationError("Failed to get PDF page count")
+            raise ResourceValidationError("Failed to get PDF page count")
 
-        if count > limit:
-            raise ValidationError(
-                f"The total number of PDF pages exceeds the limit ({limit})"
+        if limit_per_document is not None and pages > limit_per_document:
+            raise ResourceValidationError(
+                f"The number of pages in the document ({pages}) exceeds the limit ({limit_per_document})"
+            )
+
+        if limit_per_request is not None and total_pages > limit_per_request:
+            raise UserError(
+                f"The total number of pages in PDF documents exceeds the limit ({limit_per_request})"
             )
 
     return validator
@@ -274,9 +292,8 @@ async def validator():
             if first is None:
                 first = name
             elif first != name:
-                raise ValidationError(
-                    f"The document type is {name!r}. "
-                    f"However, one of the documents processed earlier was of {first!r} type. "
+                raise UserError(
+                    f"Found documents of types {name!r} and {first!r}. "
                     "Only one type of document is supported at a time."
                 )
 
diff --git a/aidial_adapter_vertexai/chat/claude/prompt/claude_3.py b/aidial_adapter_vertexai/chat/claude/prompt/claude_3.py
index d154253..d63c173 100644
--- a/aidial_adapter_vertexai/chat/claude/prompt/claude_3.py
+++ b/aidial_adapter_vertexai/chat/claude/prompt/claude_3.py
@@ -95,7 +95,7 @@ def _create_image_processor(max_count: int) -> AttachmentProcessor:
     # NOTE: not checked condition: The maximum allowed image file size is 5 MB
     return AttachmentProcessor(
         file_types=SUPPORTED_IMAGE_TYPES,
-        init_validator=max_count_validator(max_count),
+        init_validator=max_count_validator("image", max_count),
     )
 
 
diff --git a/aidial_adapter_vertexai/chat/gemini/processors.py b/aidial_adapter_vertexai/chat/gemini/processors.py
index 1f57bb4..35b6a97 100644
--- a/aidial_adapter_vertexai/chat/gemini/processors.py
+++ b/aidial_adapter_vertexai/chat/gemini/processors.py
@@ -62,7 +62,7 @@ def get_image_processor(
             "image/heif": "heif",
         },
         init_validator=seq_validators(
-            init_validator, max_count_validator(max_count)
+            init_validator, max_count_validator("image", max_count)
         ),
     )
 
@@ -91,16 +91,22 @@ def get_audio_processor(
 
 # PDF processing
 # 1.0: max number of PDF pages: 16
-# 1.5: max number of PDF pages: 300
+# 1.5: max number of PDF pages: 1000
 # The maximum file size for a PDF is 50MB (not checked).
 # PDF pages are treated as individual images.
 def get_pdf_processor(
-    max_page_count: int, init_validator: InitValidator | None = None
+    *,
+    page_limit_per_document: int | None = None,
+    page_limit_per_request: int | None = None,
+    init_validator: InitValidator | None = None,
 ) -> AttachmentProcessor:
     return AttachmentProcessor(
         file_types={"application/pdf": "pdf"},
         init_validator=init_validator,
-        post_validator=max_pdf_page_count_validator(max_page_count),
+        post_validator=max_pdf_page_count_validator(
+            limit_per_request=page_limit_per_request,
+            limit_per_document=page_limit_per_document,
+        ),
     )
 
 
@@ -134,6 +140,6 @@ def get_video_processor(
             "video/3gpp": "3gpp",
         },
         init_validator=seq_validators(
-            init_validator, max_count_validator(max_count)
+            init_validator, max_count_validator("video", max_count)
         ),
     )
diff --git a/aidial_adapter_vertexai/chat/gemini/prompt/gemini_1_0_pro_vision.py b/aidial_adapter_vertexai/chat/gemini/prompt/gemini_1_0_pro_vision.py
index 14a0e72..cb98c88 100644
--- a/aidial_adapter_vertexai/chat/gemini/prompt/gemini_1_0_pro_vision.py
+++ b/aidial_adapter_vertexai/chat/gemini/prompt/gemini_1_0_pro_vision.py
@@ -53,7 +53,11 @@ async def parse(
             processors=[
                 get_plain_text_processor(),
                 get_image_processor(16, exclusive("image")),
-                get_pdf_processor(16, exclusive("pdf")),
+                get_pdf_processor(
+                    page_limit_per_request=16,
+                    page_limit_per_document=16,
+                    init_validator=exclusive("pdf"),
+                ),
                 get_video_processor(1, exclusive("video")),
             ],
             file_storage=file_storage,
diff --git a/aidial_adapter_vertexai/chat/gemini/prompt/gemini_1_5.py b/aidial_adapter_vertexai/chat/gemini/prompt/gemini_1_5.py
index 7ac8a00..45d8b0b 100644
--- a/aidial_adapter_vertexai/chat/gemini/prompt/gemini_1_5.py
+++ b/aidial_adapter_vertexai/chat/gemini/prompt/gemini_1_5.py
@@ -45,7 +45,10 @@ async def parse(
             processors=[
                 get_plain_text_processor(),
                 get_image_processor(3000),
-                get_pdf_processor(300),
+                get_pdf_processor(
+                    page_limit_per_request=3000,
+                    page_limit_per_document=1000,
+                ),
                 get_video_processor(10),
                 get_audio_processor(),
             ],
diff --git a/aidial_adapter_vertexai/chat/gemini/prompt/gemini_2.py b/aidial_adapter_vertexai/chat/gemini/prompt/gemini_2.py
index e98ff87..d0809a6 100644
--- a/aidial_adapter_vertexai/chat/gemini/prompt/gemini_2.py
+++ b/aidial_adapter_vertexai/chat/gemini/prompt/gemini_2.py
@@ -49,7 +49,10 @@ async def parse(
             processors=[
                 get_plain_text_processor(),
                 get_image_processor(3000),
-                get_pdf_processor(300),
+                get_pdf_processor(
+                    page_limit_per_request=3000,
+                    page_limit_per_document=1000,
+                ),
                 get_video_processor(10),
                 get_audio_processor(),
             ],
diff --git a/pyproject.toml b/pyproject.toml
index 11abcf4..2fa6e03 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -53,7 +53,7 @@ nox = "^2023.4.22"
 google-auth-oauthlib = "1.0.0"
 
 [tool.pytest.ini_options]
-addopts = "-n=auto --asyncio-mode=auto"
+addopts = "-n=auto --asyncio-mode=auto --self-contained-html --html=pytest.html"
 env_override_existing_values = 1
 filterwarnings = [
     # muting warnings from google.rpc https://github.com/googleapis/google-cloud-python/issues/11184 and opentelemetry packages
diff --git a/tests/integration_tests/test_chat_completion_validation.py b/tests/integration_tests/test_chat_completion_validation.py
index 33373b4..1eb5187 100644
--- a/tests/integration_tests/test_chat_completion_validation.py
+++ b/tests/integration_tests/test_chat_completion_validation.py
@@ -7,6 +7,7 @@
 from openai.types.chat import ChatCompletionMessageParam
 
 from aidial_adapter_vertexai.deployments import ChatCompletionDeployment
+from aidial_adapter_vertexai.utils.resource import Resource
 from tests.utils.openai import (
     ChatCompletionResult,
     ai,
@@ -14,7 +15,9 @@
     sanitize_test_name,
     sys,
     user,
+    user_with_attachment_data,
 )
+from tests.utils.pdf import gen_pdf
 
 deployments = [
     ChatCompletionDeployment.CHAT_BISON_1,
@@ -167,3 +170,49 @@ async def test_imagen_content_filtering(get_openai_client):
         resp["error"]["message"]
         == "The response is blocked, as it may violate our policies."
     )
+
+
+async def test_gemini_pdf_page_overflow_for_document(get_openai_client):
+    client = get_openai_client(ChatCompletionDeployment.GEMINI_PRO_1_5_V2.value)
+
+    doc = Resource(type="application/pdf", data=gen_pdf(["a"] * 2_000))
+
+    messages: List[ChatCompletionMessageParam] = [
+        user_with_attachment_data("test", doc)
+    ]
+
+    with pytest.raises(Exception) as exc_info:
+        await chat_completion(
+            client, messages, False, None, None, None, None, None, None
+        )
+
+    assert isinstance(exc_info.value, UnprocessableEntityError)
+
+    error = exc_info.value.response.json()["error"]
+    expected_message = "The following files failed to process:\n1. data attachment: the number of pages in the document (2000) exceeds the limit (1000)"
+    assert error["message"] == expected_message
+    assert error["display_message"] == expected_message
+
+
+async def test_gemini_pdf_page_overflow_for_request(get_openai_client):
+    client = get_openai_client(ChatCompletionDeployment.GEMINI_PRO_1_5_V2.value)
+
+    doc = Resource(type="application/pdf", data=gen_pdf(["a"] * 1_000))
+
+    messages: List[ChatCompletionMessageParam] = [
+        user_with_attachment_data("test", doc, doc, doc, doc)
+    ]
+
+    with pytest.raises(Exception) as exc_info:
+        await chat_completion(
+            client, messages, False, None, None, None, None, None, None
+        )
+
+    assert isinstance(exc_info.value, UnprocessableEntityError)
+
+    error = exc_info.value.response.json()["error"]
+    expected_message = (
+        "The total number of pages in PDF documents exceeds the limit (3000)"
+    )
+    assert error["message"] == expected_message
+    assert error["display_message"] == expected_message
diff --git a/tests/utils/openai.py b/tests/utils/openai.py
index 523c2ab..7b8b34f 100644
--- a/tests/utils/openai.py
+++ b/tests/utils/openai.py
@@ -73,14 +73,14 @@ def user(
 
 
 def user_with_attachment_data(
-    content: str, resource: Resource
+    content: str, *resource: Resource
 ) -> ChatCompletionUserMessageParam:
     return {
         "role": "user",
         "content": content,
         "custom_content": {  # type: ignore
             "attachments": [
-                {"type": resource.type, "data": resource.data_base64}
+                {"type": r.type, "data": r.data_base64} for r in resource
             ]
         },
     }
diff --git a/tests/utils/pdf.py b/tests/utils/pdf.py
new file mode 100644
index 0000000..5f49378
--- /dev/null
+++ b/tests/utils/pdf.py
@@ -0,0 +1,64 @@
+from io import BytesIO
+from typing import List
+
+from pypdf import PageObject, PdfWriter
+from pypdf.generic import DecodedStreamObject, DictionaryObject, NameObject
+
+
+def _escape_pdf_string(s: str) -> str:
+    return s.replace("\\", "\\\\").replace("(", "\\(").replace(")", "\\)")
+
+
+def _create_page_with_text(
+    text: str, width: int = 612, height: int = 792
+) -> PageObject:
+    page = PageObject.create_blank_page(width=width, height=height)
+
+    content_stream = "BT\n"
+    content_stream += "/F1 12 Tf\n"
+
+    x = 72
+    y = height - 72
+
+    for line in text.splitlines():
+        content_stream += f"{x} {y} Td\n"
+        content_stream += f"({_escape_pdf_string(line)}) Tj\n"
+        y -= 14
+    content_stream += "ET\n"
+
+    stream = DecodedStreamObject()
+    stream.set_data(content_stream.encode("utf-8"))
+    page[NameObject("/Contents")] = stream
+
+    resources = DictionaryObject()
+    font_dict = DictionaryObject()
+    font = DictionaryObject(
+        {
+            NameObject("/Type"): NameObject("/Font"),
+            NameObject("/Subtype"): NameObject("/Type1"),
+            NameObject("/BaseFont"): NameObject("/Helvetica"),
+        }
+    )
+    font_dict[NameObject("/F1")] = font
+    resources[NameObject("/Font")] = font_dict
+    page[NameObject("/Resources")] = resources
+
+    return page
+
+
+def gen_pdf(pages: List[str]) -> bytes:
+    """
+    Generate a PDF from a list of page strings.
+    """
+    writer = PdfWriter()
+
+    for text in pages:
+        page = _create_page_with_text(text)
+        writer.add_page(page)
+
+    output = BytesIO()
+    writer.write(output)
+    pdf_bytes = output.getvalue()
+    output.close()
+
+    return pdf_bytes