How to fill in and compare PDF forms

Last updated: 19 October 2026

Fillable PDF forms are used for applications, order forms, onboarding packs and contract annexes. When a form comes back filled in, the important question is what the other person entered, and whether it matches what was agreed.

Compare the field values

Open the blank or previously approved form as the reference and the returned form as the checked PDF. compare2pdf reads every text field, checkbox, radio button and drop-down list in both files and lists each value that differs as a Form field finding, showing the old and the new value.

Correct fields directly

Fields in the checked PDF are editable. Click a text field to type, tick or clear checkboxes and choose options from drop-down lists. Edited fields are highlighted so you can see what you changed, and the findings list updates as you edit.

Undo and redo

Every edit is recorded. Use the undo and redo buttons in the toolbar, or press Ctrl+Z and Ctrl+Shift+Z when you are not typing inside a field.

Save the updated form

Click Save PDF to download the form with your changes. The fields stay fillable, so the next person can continue editing in any PDF reader.

Good to know

• Read-only fields are shown but cannot be edited.
• Signature fields are not editable in the browser.
• Some PDF readers redraw field text with their own fonts. If a value with special characters looks different in another reader, click into the field and it will display correctly.