What PDF compression can do to signatures, forms, links, and bookmarks

Digital signatures are sensitive to modification

A cryptographic signature protects a specific version of a document. Changing page streams, metadata, or structure can make the signature invalid even when the visible page looks identical.

Keep the signed original. If a smaller copy is needed only for reference, label it clearly and confirm that the receiving party accepts an unsigned derivative.

Rendering can flatten interactive features

Balanced and Maximum may render pages as images. Form fields, selectable text, annotations, layers, and clickable links can become ordinary pixels.

Lossless is less disruptive but cannot guarantee that every complex PDF feature survives. PDF implementations and source files vary.

Test beyond appearance

If the workflow depends on an interactive feature, use the original unless the output passes every relevant test.

• Open the signature panel and check validation status.
• Tab through every required form field.
• Click external and internal links.
• Open the bookmark panel.
• Test copy and search for text.
• Check screen-reader behavior when accessibility matters.