What is PDF form flattening?
Definition
Form flattening converts a filled PDF's interactive fields into fixed page content: the values are painted onto the page and the editable fields are removed. The result looks identical but can no longer be changed or read back as form data.
What flattening does
Before flattening, a value lives in an editable field that anyone can alter. After flattening, that value is part of the page image, locked in place, like ink on paper. The document is no longer a form, just a finished page.
When to flatten
Flatten when a form is final and should not be edited further: an executed agreement, a submitted application, an archived record. Keep fields interactive while the form is still being completed or reviewed.