Check whether a PDF's digital signatures still hold, who made them, and what changed after. Free, with no account or uploads.
Drop a signed PDF to check its signatures
Each signature is checked on your device: whether it still holds, whose certificate made it, when it says it was made, and what was added to the file after it. You can also paste a file with ⌘V or Ctrl+V.
PDF
Stays on your device · up to 300 MB
Off, nothing is kept: closing the tab loses changes that were not downloaded. On, the file and your changes are kept in this browser until you close the file or throw the draft away. Nothing is sent anywhere.
What you can do
Does it still hold?Each digital signature is checked against the bytes it covers: changed by even one byte, and it does not hold.
Who, and whenThe certificate that signed, who issued it or that it signed itself, and the time the signature gives. Add the issuers you trust, and each signature says whether it goes back to one.
What changed afterA file signed and then added to is laid beside the version that was signed: fields filled in, comments, pages that look different, signatures added later.
Nothing is uploadedThe file is read and its signatures checked on your device.
This is the PDF editor, opened for checking signatures. Its other tools (text, pictures, forms, and signing with a certificate at download) are behind “All tools”.
A little help along the way
Follow the steps below. Every option is explained underneath.
27 s, no sound. On-screen captions describe each step; the same steps are written out here.
1Open the signed PDFDrop it, choose it from your device or paste it. A locked file asks for its password. The list of its signatures opens beside the pages.
2Read what each saysEach signature says whether it holds, whose certificate made it and who issued that, when it says it was signed, and its reason and place if it gives them.
3See what changed afterA file can be added to after it is signed, as when a second person fills in a field or signs too. The list says what was added after each signature: fields, comments, pages that look different, other signatures.
4Show it on the pageA signature that shows on a page has a button that goes to it.
Every option explained
Holds, or does not
A signature covers the bytes of the file as it was signed. If one of them was changed afterwards, it does not hold, and the list says so. Additions written after a signature (a second version of the file) do not break it; the list says what they changed.
Whom to trust
A signature is made with a certificate, and a certificate names a person or a company. Whether that name can be believed depends on who issued the certificate. KeepSimp says who did, or that the certificate signed itself, and keeps no list of trusted issuers of its own, as Adobe's programs do. Under “Certificates you trust” you can add the certificate of an issuer you trust, such as your company's, from a .cer, .crt, .der or .pem file; each signature then says whether its certificate goes back to it, through certificates that each issued the next and were valid at the time it gives. Add only a certificate you got from someone you trust, never one from the file you are checking. The list lasts while the page is open, or stays on this device when “Remember them on this device” is on. A certificate that signed itself vouches for nobody unless you trust it.
The time a signature gives
It is the time on the clock of the device that signed. Without a time stamp from a time-stamping authority, which is not checked here, it is not proved.
Kinds of signature
Signatures of the kinds adbe.pkcs7.detached, ETSI.CAdES.detached and adbe.pkcs7.sha1 are checked; that covers what Acrobat, other programs and KeepSimp make. Older kinds and document time stamps are listed but not checked, and say so.
Your changes
The list is of the file as it was opened. Changes you make in the editor are written after the signatures when you download with “Keep it valid”, and the signatures still hold over what they signed.
All tools
This page is the PDF editor, opened for checking signatures. All tools shows the rest, and you can sign with your own certificate when you download.