Native watermark flattening causes massive file size explosion and layer corruption in Acrobat Pro 2020
Steps to reproduce the issue
1. Open a standard text/vector PDF (approx. 2,000 KB).
2. Go to Tools > Edit PDF > Watermark > Add, and apply a text watermark.
3. Attempt to flatten or permanently bake the watermark into the document using standard workflows (e.g., Save As Optimized PDF, Print to PDF, or running the Preflight "Flatten annotations and form fields" fixup).
4. Inspect the resulting file size and test the watermark object with the Edit tool.
Environment (OS, other related application versions, etc.)
Application: Adobe Acrobat Pro 2020 (Classic Desktop Edition)
OS: Windows / macOS (Note: You can specify your exact OS here if you'd like)
Trigger: Initiated following recent background security/compatibility patches to Acrobat 2020.
Expected result
The watermark layer should merge natively with the existing document content streams. The file size should remain low (under 1 MB), and the watermark text should become completely unselectable and unremovable.
Observed result
Acrobat either fails to lock the watermark layer entirely (leaving it fully editable/removable), or it forcefully rasterizes the overlapping background text layers into uncompressed bitmap images. This causes the file size to balloon exponentially from ~600 KB to anywhere between 14,000 KB and 103,000 KB, making basic document emailing impossible.
Christel Whetstone
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