How to tell if a PDF has been editedProperties are clues; the reliable check is a comparison with the original

Clues inside the file, and checks outside it

Open the document properties in your PDF reader. They often list a creation date, a modified date and the program that produced the file. A modified date that is later than the creation date, or a producer such as an image or PDF editor, can be a clue that the file was changed. But these fields are easy to edit or strip, and many harmless steps (printing to PDF, compressing, signing) rewrite them. They are clues, not proof either way.

Stronger checks come from outside the file. Ask the sender for the original, or get the document from its source again, then compare the two. A cryptographic hash of each file will differ if even one byte differs; our file comparison checker does this in your browser without uploading either file. A match shows the files are identical. A mismatch shows they differ, not which one is right or what changed.

If the PDF carries a digital signature, your reader can report whether the signed content has changed since signing and who the certificate names. An unsigned PDF has no such check. For read-only visual checks, look for mismatched fonts, spacing or compression around names, dates and amounts, and check the details with the issuer directly.