Chore: Consolidate test sample files (#14430)

Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>

src/documents/tests/utils.py

@@ -11,6 +11,7 @@ from documents.data_models import ConsumableDocument
 from documents.data_models import DocumentMetadataOverrides
 from documents.data_models import DocumentSource
 from paperless_testing.fakes.progress import FakeProgressManager
+from paperless_testing.samples import SIMPLE_DIGITAL_PDF
 
 
 class ConsumeTaskMixin:
@@ -53,6 +54,8 @@ class SampleDirMixin:
 
     BARCODE_SAMPLE_DIR = SAMPLE_DIR / "barcodes"
 
+    SIMPLE_PDF = SIMPLE_DIGITAL_PDF
+
 
 class GetConsumerMixin:
     @contextmanager