Repair PDF
Fix corrupted or damaged PDF files. Rebuilds structure, recovers pages, and restores content.
What this tool does:
- Fixes broken cross-reference tables
- Recovers damaged page structures
- Re-linearizes for faster web viewing
- Removes unused objects and garbage data
PDF Repair
Upload a damaged PDF to attempt recovery
How It Works
Upload your broken PDF
Drop in the corrupted or unreadable PDF file. Up to 25 MB on the free plan.
AI repair process
Our repair engine rebuilds the PDF structure — reconstructing cross-reference tables, recovering embedded objects, and fixing encoding errors.
Download the fixed PDF
Download the repaired PDF and verify all content is accessible.
Why SynthPDF?
Rebuilds PDF structure
Reconstructs the cross-reference table and object index that PDF readers depend on — the most common source of 'cannot open PDF' errors.
Recovers pages and images
Extracts recoverable page objects from damaged files, even when the directory structure is missing.
Handles truncated files
PDFs that were cut off mid-download or mid-write are often partially recoverable — we extract what's intact.
Server-processed safely
Files are processed over HTTPS and deleted within 30 minutes. We do not read or retain document content.
Free for files up to 25 MB
Repair PDFs up to 25 MB on the free plan. Pro plan supports up to 100 MB.
Repair report included
After repair, you receive a summary of what was found and recovered — and what could not be restored.
Why PDFs Get Corrupted
PDF files are structured documents — they have a header, body of objects (pages, fonts, images), a cross-reference table (index of all objects), and a trailer. When any of these are incomplete or damaged, the PDF reader cannot interpret the file and reports an error.
The most common causes:
- Interrupted download — the file is truncated partway through transfer
- Drive failure or bad sectors — physical damage to storage corrupts the file data
- Failed export — a crash during "Save as PDF" in Word, Chrome, or another app
- Email corruption — some email servers or antivirus tools modify attachments
- Version incompatibility — older PDF readers failing on newer PDF format features
What the Repair Process Does
Our repair engine attempts three recovery strategies, in order:
- XRef rebuild — reconstructs the cross-reference table by scanning the file body for valid object definitions
- Object extraction — pulls page objects, fonts, and images directly from the raw file bytes, bypassing the directory
- Stream repair — attempts to decompress and recover compressed content streams with partial data
When Repair Won't Work
Some files are too damaged to recover useful content from:
- Files overwritten with zeros (deleted and partially overwritten on a hard drive)
- Files encrypted with an unknown password
- Files where page content streams are completely absent (only structural metadata remains)
- Severely fragmented files from a failed RAID or SSD
If our tool cannot recover your PDF, the next step is professional data recovery software (such as PDF Repair Toolbox or Stellar Repair for PDF) which uses more aggressive recovery algorithms.
Prevention: How to Avoid PDF Corruption
- Always wait for downloads to complete before closing your browser
- Verify file size after download — a 2 MB PDF shouldn't be 20 KB
- Keep backups of important PDFs in cloud storage
- Don't open PDFs from untrusted sources — some may exploit PDF parser bugs
Frequently Asked Questions
Cross-reference table errors, truncated files, encoding issues, missing end-of-file markers, and damaged object streams. Severely overwritten or physically damaged storage media may be unrecoverable.
Most content is recovered from common corruption types. Partially overwritten files may recover some pages but not others.
Common causes: interrupted download (file truncated mid-transfer), storage drive failure, email attachment corruption, failed export from another application, or antivirus software modifying the file.
Only if you know the password. The repair process requires reading the file structure, which requires decryption.
Garbled text is usually a font encoding issue, not corruption. Use our PDF to Text tool to extract the raw text, which bypasses font rendering issues.