Digital Signatures in PDFs

In recent years most companies switched to different methods of electronic document management. This allows to drastically shorten time for business clearance, simplifies document accounting and archiving. But electronic document management also rises the issue of documents authenticity and validation.

Digital signature is an effective way to protect document from changes and identify true sender.

Digital signature ensures that signed document wasn’t changed by anyone other than its author. It is most common way to authenticate document content. PDF signature has digital certificate, provided by trusted certificate center.

Master PDF Editor allows to validate digital signatures, create them and sign documents.

Creating Signature and Sign a PDF document

Document is signed after editing. If the document is modified after signing, these changes will corrupt the signature.

In order to create a signature, you must own a digital certificate. It is common to work with certificates provided by Certificate Authorities which act as trusted third party. They issue and validate certificates as owned by certain person or entity. Depending on local law, such validation might allow to receive authentic information about signer.

In Mac and Windows certificate must be previously copied to system certificate storage. With Linux you have to import certificate into Certificate Manager beforehand.

Perform following actions to create a digital certificate:

  • Choose Forms > Signature in Main menu or click  Signature button on the toolbar. In a document, choose a rectangle where digital signature must be located.

If you have a digital certificate, you can sign the document. Do the following:

  • Choose Tools >Hand Tool in Main menu or press  Hand Tool (Alt+4) button on the toolbar. To create a signature left click a signature form. (If Edit Document  or Edit Forms is selected, left click twice) When Signature Properties window has popped up, choose required certificate in Sign As field.

  • Press Sign button.

In macOS and Windows you’ll have to permit the application to access certificate storage. When signing, you’ll be prompted for file name and location. Choose file name to sign and save PDF document.


Digital Signature Validation

Master PDF Editor can be used to validate signatures in PDF files. If Edit Document  or Edit Forms tool is on, double click certificate or click it once if Hand Tool is on. You’ll see a window with certificate validation result.

Results of the certificate validation may be one of the following

  • Signature is VALID – Signature is valid, document wasn’t changed after signing and certificate was provided by trusted certification center.
  • Signature is INVALID – Issues occurred when validating the signature. Document was changed or damaged after signing.
  • Signature validity is UNKNOWN – Signature is valid, document wasn’t changed after signing, but certificate isn’t trusted.


To make certificate trusted:

For Windows and Mac OS X: You must add certificate’s open key to system certificate storage.

For Linux: Press Information button, view certificate properties and then press Add to Trusted Identities button.


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