pdf Integrated PDF signatures 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.)