Repair PDF
Some PDFs break in transit. Some break at upload. Some break in archival storage.
We try to save what we can — and we tell you honestly what we couldn't.
Drop your damaged PDF here
Fully repaired
Low — clean recovery
pdf-lib loaded your file with zero parser warnings. The output should render identically to a non-broken PDF.
Partially recovered
Medium — some content affected
Some objects were dropped during parse. The output is usable but verify it matches your expectations. The warnings inventory below shows what was affected.
View parser warnings (0)
Structural recovery only
High — content rendering uncertain
The tool rebuilt a missing header before loading. The file structure is valid but content rendering is uncertain. If the output doesn't display correctly, try PDF to Text for content extraction.
View parser warnings (0)
About PDF repair
How PDFs typically break
Email transit truncation is the most common cause: SMTP servers cut large attachments mid-file, leaving the PDF without its trailing bytes. Network interruptions during download produce the same shape. Scanner firmware bugs (Xerox, Canon, HP) write malformed xref tables — the document is structurally invalid but page content is intact. Archival PDFs from 1998-2003 used pre-spec-clarification headers that strict parsers now reject. PDFs concatenated with garbage from email-system bounces are surprisingly common. Each of these classes has a recovery path; the tool reports which one applied and how complete the result is.
What can be repaired
pdf-lib's loose-parse mode handles five corruption classes natively: garbage between indirect objects, missing xref cross-reference sections, missing trailer dictionaries, broken catalog Root references (the tool re-scans the document for a valid catalog), and invalid indirect objects (the tool skips them and continues). For a missing PDF header signature, the tool scans the first 1024 bytes for an embedded signature and retries the load from there. Custom non-standard structures from old scanner firmware often parse cleanly because the loose mode is intentionally tolerant.
What we can't repair
Encrypted PDFs without the password cannot be repaired — the file contents are encrypted along with the structural metadata. Remove the password in your PDF software first, then upload. Files that are not PDFs at all (e.g., text or image files renamed to .pdf) are detected at pre-flight by checking for the %PDF magic bytes. Files where the parser stalls completely (typically large truncation losing >50% of bytes) cannot be salvaged structurally. For unrepairable-total-loss cases, PDF to Text may still extract any plain-text content as a last resort.
Three outcome modes explained
Fully repaired means pdf-lib loaded the document cleanly with zero parser warnings — the output PDF should render identically to a non-broken PDF. Partially recovered means pdf-lib emitted at least one warning during parse (invalid objects skipped, broken references recovered) — the output is usable but some objects may have been dropped; the warnings inventory shows which. Structural recovery only means the tool had to rebuild a missing header before loading — the file structure is valid but content rendering is uncertain; consider PDF to Text as a fallback if content doesn't render correctly. After any successful outcome, Compress PDF may help if file size matters before sharing.
Why browser-only repair matters
Damaged PDFs often contain the content you most want to recover — financial statements that got truncated mid-transfer, legal drafts from a scanner that misfired, archival records from a long-defunct system. Uploading those to a third-party server at the exact moment you can't open them adds risk: you don't know what's inside the damaged bytes, and neither does the server. pdfmundo's repair runs entirely in your browser via pdf-lib. The damaged file never leaves your device. Competing tools either upload to servers (Sejda, PDF24) or paywall behind subscriptions (PDFCandy, Adobe). pdfmundo ships free, unlimited, browser-only.
Frequently asked questions
- What kinds of corruption can be repaired?
- pdf-lib's loose-parse mode covers five corruption classes natively: garbage between indirect objects, missing xref sections, missing trailer dictionaries, broken catalog references, and invalid indirect objects. The tool adds two more recovery paths: pre-flight detection of non-PDF files and a header-rebuild retry that scans the first 1024 bytes for a misplaced PDF signature. Files with encryption you can't decrypt or with total content destruction cannot be repaired.
- Will repair lose any of my content?
- Fully repaired means zero content loss — the output renders identically to an undamaged PDF. Partially recovered means some invalid objects were dropped during parse — typically embedded fonts or images that pdf-lib couldn't decode. The page content text usually survives. Structural recovery only means the tool rebuilt a missing header before loading — content rendering is uncertain. The warnings inventory in the result panel shows exactly which objects were affected.
- Why can't you repair encrypted PDFs?
- Encryption is layered above the document structure. Without the password, the Info Dictionary and content streams are unreadable, including the structural metadata the repair tool needs to attempt recovery. Remove the password in your PDF software first (if you know it), then come back here.
- What does 'partially recovered' mean?
- pdf-lib emitted at least one parser warning during the load — typically that a specific indirect object couldn't be parsed (and was skipped), or that a broken reference was recovered to a different target. The output PDF is usable but some objects may have been dropped. The warnings inventory in the result panel lists every warning the parser emitted, so you can verify what was affected.
- Is my damaged file uploaded to your servers?
- No. Repair runs entirely in your browser. The damaged file stays on your device. This matters specifically for repair: damaged PDFs often contain the content you're most concerned about, and competing tools either upload to servers or paywall behind subscriptions. pdfmundo ships free, unlimited, browser-only.
- What if the repaired file still won't open?
- Some PDFs are damaged beyond browser-side recovery. If the repaired file still fails to open in a PDF reader: try a different reader (Adobe Reader, Preview, Firefox built-in viewer), or use PDF to Text as a last-resort content extraction. PDF to Text reads at a different abstraction level and may recover plain-text content even when full PDF rendering fails.
- How large a file can I repair?
- Up to 50 MB. The same cap applies to Edit Metadata, Crop PDF, Reorder Pages, Rotate, Delete Pages, Extract Pages, Page Numbers, and Watermark. For damaged files larger than 50 MB, the constraint is browser memory: pdf-lib's parse cost scales with file size, and the in-browser engine becomes unreliable above the cap.
- What's the difference between 'fully repaired' and 'partially recovered'?
- Fully repaired means zero pdf-lib warnings during the load. Partially recovered means at least one warning fired — the parser found something it couldn't fully handle but routed around it. Both produce a usable output PDF; partially recovered just signals that you should verify the content matches your expectations. The warnings inventory shows what specifically was affected.
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