Repair PDF

What it can fix

The rebuild handles the common structural faults: a cross-reference table that points to the wrong place, a missing trailer or end-of-file marker, a file cut off after the last complete object, and stray bytes before the %PDF header such as an HTTP response or an email envelope. In these cases text, fonts, images, links and form fields come back exactly as they were, because the objects themselves were intact.

• Wrong or missing cross-reference table
• Missing trailer or end-of-file marker
• Junk before the header
• Truncated file, when the page objects survived

The rescue mode

If the page objects themselves are damaged, a rebuild is not possible. PaperKit then asks pdf.js, a very forgiving renderer, to draw whatever pages it can still find and saves those drawings as a new PDF. You get the pages back as images at 150 dpi: readable and printable, but the text is no longer selectable. The result card says clearly which of the two paths was used, and OCR PDF can make a rescued file searchable again.

What it cannot fix

Data that is not in the file cannot be recovered. If a download stopped halfway, the pages in the missing half are gone and only the first pages return. A file that is zero bytes, or that is not a PDF at all despite its name, cannot be repaired; the tool says so. Password-protected PDFs need to be unlocked first, since their contents cannot be read without the password.

Reading the diagnosis

Before rebuilding, PaperKit checks four things and reports what it found: where the %PDF header is, whether the end-of-file marker is present, whether the pointer to the cross-reference table exists, and whether that pointer leads to a table. A file with none of these problems is simply rewritten cleanly, which also helps with documents some strict readers reject for minor violations.

After repairing

Open paperkit-repaired.pdf and page through it; the PaperKit PDF Viewer works for this. Compare the page count with what you expected. If the original came from an application you still have, exporting it again remains the most reliable fix. Keep the damaged file until you are satisfied with the result.