pdf Allowed and disallowed changes to a signed document


Example

In the Adobe technical white paper Adobe Acrobat 9 Digital Signatures, Changes and Improvements, especially its section "Allowed and disallowed changes", Adobe clarifies the allowed changes (as seen by Acrobat 9 and up) that can be made to a certified or signed document without invalidating the signatures applied to the document.

Allowed actions for certified documents

Certified with no changes allowed

Allowed

  • No changes allowed

Disallowed

  • Digitally signing
  • Supplying form field values
  • Adding or editing annotations
  • Adding form fields
  • Changing page content

Certified with form fill-in and digital signatures allowed

Allowed

  • Supplying form field values
  • Digitally signing

Disallowed

  • Adding or editing annotations
  • Adding form fields
  • Changing page content

Certified with annotations, form fill-in, and digital signatures, allowed

Allowed

  • Adding or editing annotations
  • Supplying form field values
  • Digitally signing

Disallowed

  • Adding form fields
  • Changing page content

Allowed actions for signed but uncertified documents

Allowed

  • Adding signature fields (see Limitations on adding signature fields to signed but uncertified documents)
  • Adding or editing annotations
  • Supplying form field values
  • Digitally signing

Disallowed

  • Adding form fields other than signature fields
  • Changing page content

(Even though not explicitly mentioned here, instantiating page templates most likely also is allowed whenever form fill-ins are allowed as that would conform to the PDF standard, cf. ISO 32000-1 section 12.8.2.2.2.)