PDF Fixer is a free utility capable of repairing corrupt PDF files by restructuring the damaged PDF data, rebuilding XREF tables, and then restores these damaged PDF documents into readable PDF files.
Some similar command-line tools include the PDF fixing function; however, they generally only fix PDF metadata errors and regenerate XREF tables. If you need to repair a severely damaged PDF file, you'll find that most others are incapable of recovering the file data and display errors. This is where PDF Fixer shines. PDF Fixer will analyze the data that still exists through the whole corrupt PDF. It then assembles objects to repair them. Best of all, no Adobe Acrobat needs to be installed for use.
PDF Fixer provides straightforward usage with minimal clicks to repair your damaged PDF file. It supports drag n' drop and works relatively fast. There is also a portable option, so you can store it on a USB when you are away from your desktop.