PDF Repair
Diagnose and recover damaged, corrupted, truncated, or unreadable PDF documents directly in your browser.
Corrupted cross-reference tables and damaged trailer dictionaries are reconstructed in local memory without uploading files.
The FileTools PDF Repair tool reconstructs damaged, corrupted, or truncated PDF documents entirely in your browser. It features a progressive multi-tier recovery pipeline: header signature normalization, cross-reference (XREF) rebuilds, trailer dictionary synthesis, integer-overflow-tolerant parsing, raw page object salvaging, and an emergency visual raster reconstruction fallback.
Key Challenges Solved
- ✓ Corrupted cross-reference tables (XREF) or damaged trailers preventing PDF files from opening.
- ✓ Download interruptions and bad byte transfers leaving PDF documents unreadable in standard readers.
- ✓ Critical historic records failing to open with 'file is damaged or corrupted' error dialogs.
Who Is PDF Repair Built For?
IT helpdesk technicians recovering unopenable email attachments and corrupted shared network files
Forensic data recovery specialists restoring damaged documents from failing storage media
Business users salvaging incomplete downloads of important financial statements and receipts
Progressive PDF Reconstruction: XREF Table Rebuilding & Stream Salvaging
How 4-tier structural repair and emergency visual rasterization recover broken documents
What We Verified
- ✓ Tier 1 Header & Trailer Normalization: Restores missing %PDF-1.x signatures and reconstructs %%EOF markers that prevent document opening in strict viewers.
- ✓ Tier 2 XREF Table Re-indexing: Rebuilds corrupted cross-reference tables and broken byte offsets by scanning binary object tags directly in RAM.
- ✓ Tier 3 Tolerant Parsing & Object Salvaging: Extracts surviving page dictionaries and indirect font objects even if trailing data was truncated during interrupted downloads.
- ✓ Tier 4 Emergency Raster Recovery: When internal dictionary corruption prevents structural parsing, Mozilla PDF.js renders intact visual pages into a pristine reconstructed PDF.
Why This Happens (Technical Architecture)
Standard PDF readers require a continuous byte offset map located in the cross-reference table (xref) and root trailer dictionary. If an email transfer truncates the file or a crash corrupts the trailer offset (startxref), readers immediately display a "file is damaged and cannot be opened" error. FileTools scans the raw binary buffer for obj ... endobj delimiters, rebuilds the internal xref lookup map, and synthesizes a valid trailer. If object trees are unrecoverable, the engine triggers an emergency canvas raster recovery pass.
Key Features & Benefits
Multi-Tier Recovery Engine
Progresses from non-destructive header normalization to stream salvaging and emergency visual recovery.
XREF & Trailer Synthesis
Rebuilds broken, offset, or missing cross-reference tables and synthesizes corrupted trailer dictionaries.
Page Stream Salvaging
Harvests uncorrupted page objects even when trailing bytes were truncated during incomplete downloads.
100% Local File Recovery
Repair proprietary documents and confidential records securely without transmitting data to remote servers.
How to Use PDF Repair
- Select or drag and drop your corrupted PDF file into the repair tool.
- Our multi-tier engine analyzes the document structure and attempts progressive recovery.
- Review the diagnosis report and download your repaired PDF.
Common Use Cases
Interrupted Download Recovery
Recover documents that were partially downloaded or truncated due to dropped connections.
Corrupt Email Attachments
Fix PDF attachments that fail to open in Adobe Acrobat with "file is damaged" errors.
Legacy & Non-Conforming PDFs
Standardize older non-conforming PDF files into valid ISO 32000 compliant documents.
Continue Your Workflow
Recommended logical next steps after using PDF Repair:
PDF Metadata Inspector
Inspect document properties, creation dates, embedded JavaScript actions, attachments, and catalog structure directly in your browser.
Use PDF Metadata Inspector →Sanitize PDF
Sanitize PDF files by neutralizing executable JavaScript, automated launch actions, tracking streams, and embedded attachments.
Use Sanitize PDF →Compress PDF
Reduce PDF file size by optimizing the document.
Use Compress PDF →You May Need This Before
Common preparation and prerequisite steps before PDF Repair:
Compress PDF Below 100KB
Compress PDF documents below 100KB online for free without losing readability for government job portals, UPSC, SSC, and TSPSC.
← Prerequisite: Compress PDF Below 100KBPDF Metadata Inspector
Inspect document properties, creation dates, embedded JavaScript actions, attachments, and catalog structure directly in your browser.
← Prerequisite: PDF Metadata InspectorProgressive Multi-Tier Recovery Pipeline
FileTools applies a 4-tier structural recovery process: Tier 1 normalizes headers and EOF trailers; Tier 2 performs tolerant parsing with pdf-lib; Tier 3 applies capNumbers integer overflow protections; Tier 4 directly extracts uncorrupted /Page streams. If structural parsing is impossible, a last-resort visual raster recovery rebuilds an image-based PDF using PDF.js rendering.
Recovering an Incomplete Scanned Tax Form
A user downloads an archived tax form that throws an XREF table error when opening in desktop viewers.
PDF Repair identifies broken trailer offsets, reconstructs the object catalog in memory, and writes a pristine document.
Important Operational Notes & Realistic Limitations
- Severely corrupted files where underlying content streams were completely overwritten with zeros cannot be reconstructed.
- Password-protected encrypted files with lost encryption keys cannot be repaired.
- Visual raster recovery produces an image-based PDF where original vector paths, interactive form fields, and selectable text streams may not be preserved.
Frequently Asked Questions
How do I repair a corrupted PDF file?
The repair tool will fix corrupted PDF files where recovery is possible. It can repair damaged PDF files, attempt to recover unreadable PDF documents, and rebuild broken cross-reference tables locally.
Why do PDF files become corrupted?
Common causes include incomplete internet downloads, email gateway encoding errors, bad storage sectors, and improper software crashes during saving.
What is the visual raster recovery fallback?
When a PDF has damaged internal dictionaries that prevent standard structural reconstruction, our engine uses PDF.js to render surviving pages to high-resolution bitmaps and bundles them into a recovered PDF document.
Are my private files sent to your servers?
No. FileTools operates completely client-side. Your documents never leave your computer or mobile device.
What types of PDF corruption can be repaired?
It rebuilds missing or damaged Cross-Reference (XREF) tables, repairs corrupted trailer dictionaries, restores stream byte offsets, and recovers page object trees. Zero-byte files or completely overwritten data cannot be restored. After repairing document structures, deep-clean unwanted scripts with Sanitize PDF (/sanitize-pdf).
Can it recover files that are zero bytes or encrypted?
No. A file must contain readable PDF object fragments. Zero-byte files or corrupted ciphertext cannot be decrypted or repaired without keys.
Is /repair-pdf the official route?
Yes, /repair-pdf is the canonical route for the FileTools PDF Repair tool. Any legacy links to /pdf-repair permanently redirect here.