Five PDF compressors tested on a signed file; two deleted the signature entirely

A developer signed a fictional one-page PDF and ran it through five common compressors, with every output failing signature validation. Four tools retained the original signature dictionary, but the byte ranges no longer matched the rewritten file, so validators judged them invalid. Two tools, Ghostscript and iLovePDF, removed the signature field altogether, producing files that show no error and may still display a visible signed-by stamp. The author notes the danger is greatest in the second case, since recipients have no reason to check. The tests found that local and cloud-based tools alike rewrote the file bytes, so the problem was not tied to where processing happened.