Getting "Format error: not a PDF"?
This often means the header bytes or internal markers are malformed, missing, or overwritten.
Common signs
- Reader says file is not a PDF
- Browser cannot render attachment
- Portal blocks upload immediately
Why this happens
Missing %PDF header signature
Binary corruption during transfer
Wrong extension on malformed export
What to do next
1
Run automated repair pass
Structural reconstruction can recover files with damaged headers and trailer data.
2
Check preview page output
Use preview to confirm readable content before unlocking full file.
3
Replace previous upload
Submit only the repaired output in your target system.
Frequently Asked Questions
Can extension-only renaming fix this?
Usually no. True format errors need structural repair, not filename changes.
What if the file was never a real PDF?
If source content is missing entirely, recovery may not be possible.
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