“Please send a flattened PDF” — a request that sounds technical but describes something simple: fusing all the editable, floating parts of a PDF into fixed page content, like laminating a filled-in form.
What flattening actually merges
Interactive form fields become printed text. Annotations, comments, and stamps become part of the page image. Layered content collapses into one layer. After flattening, what you see is permanently what anyone gets — nothing can be toggled, edited, or peeled off.
When to flatten
Submitting completed forms: flatten after filling a PDF form so answers cannot be altered downstream (the fill tool has this built in). Finalizing reviewed documents: annotations from a review round fuse into an unambiguous final. Preparing for print: print workflows prefer flattened files because interactive elements render inconsistently. Sharing edited files: whiteout and text placed with a PDF editor become tamper-resistant once flattened.
When NOT to flatten
Never flatten the only copy of a form others still need to fill. Never flatten a document mid-review — comments stop being removable. Flattening is one-way; keep the interactive original archived and share the flattened copy, a habit the privacy guide endorses for sensitive material.