Upload a PDF that won't open or throws an error, and this attempts to rebuild it page by page, recovering as many readable pages as possible into a fresh, working file.
An interrupted download, a browser crash mid-save, or a bad transfer over an unstable connection are the usual culprits. The internal structure a reader expects ends up scrambled, even though the actual page content is often still intact underneath.
It goes through the file page by page, copying each one into a freshly built document rather than trying to patch the damaged file in place. Pages that copy successfully make it in; pages that can't be salvaged get reported separately, so you know exactly what came through.
Not always. Recovery depends on how the file was corrupted, and the tool reports exactly how many pages it could and couldn't save.
Yes, your original is never modified or deleted. The tool only reads it and produces a separate repaired copy.
Interrupted downloads, crashed apps mid-save, storage errors. Repair works regardless of the original cause.
If you still have access to the source (the scanner, or whoever sent it), re-generating just those pages is usually more reliable than reconstructing badly damaged data.