PDF is a very common document format in our daily work. It is a binary coding format generated by virtual printing of various files. Since most of PDF data is compressed, editing PDF files with a text editor will cause file corruption or data offset, or lose part of the data due to network instability during network transfer, which will cause PDF files to be damaged and corrupt. PDF reader programs cannot open or repair those corrupt PDF files and would prompt a few error alerts.
PDF Fixer is a free PDF repair utility which repairs corrupt PDF files by restructuring the damaged PDF data, rebuilding XREF tables and then restore these damaged PDF documents into readable PDF files.
PDFTK (PDF Toolkit) and Ghostscript are two free PDF command-line tools and both of them have the PDF repair function, but PDFTK can only repair PDF information problems, while Ghostscript can only regenerate XREF tables. Once you need to repair a really damaged PDF document, you will find that neither PDFTK nor Ghostscript can recover the file data:
(Download the corrupt PDF sample file - a broken manual PDF from SoX)
PDFTK failed to repair the corrupt PDF:
Ghostscript failed to repair the corrupt PDF:
But don't worry, no matter how badly the PDF file is broken, PDF Fixer can analyze the data that still exists and assemble all objects then repair the PDF out: