Locking a form's answers and a draft's comments in place
A filled-in form field, a highlight or a sticky note sits on top of a PDF's page as a separate layer, and any PDF editor can change or delete it. Flattening draws each of them into the page, exactly as it looks, and removes the layer. The page looks the same afterwards; what changes is that nobody can edit the answers or the comments any more.
Updated
Which tool you need
You filled in a form and are sending it back
Flatten the form fields, so the answers you typed read the same for everyone and cannot be changed after you send it.
A reviewed draft with comments you want to keep visible
Flatten comments and markup. The highlights and notes become part of the page and travel with it, in every viewer.
A document with names or numbers that must not be readable
Not flattening. Flattening keeps everything visible; hiding text needs redaction, which takes the words out of the page itself.
You also want the author and hidden data gone
Remove PDF Metadata clears the properties and hidden data after you flatten.
Flatten before you sign
A certificate-backed digital signature is only valid while the file is unchanged, and flattening changes it. Flatten first, then sign. A signature drawn or typed with Sign PDF is a picture on the page and flattens like anything else.
What a sticky note becomes
Highlights, stamps, underlines and drawings flatten into exactly what they showed. A sticky note is different: what it shows on the page is its small icon, so the icon is drawn in, while the text typed inside it, which opened in a pop-up, does not come across.
So read through the notes first, and move any words that matter into the document itself. A comment the file marks as hidden is removed rather than drawn, and the result counts it.
Forms filled in by another app
Some apps save a form's typed answers without drawing them, and leave that to whichever viewer opens the file next. Before such a form is flattened, its text boxes, dropdowns and lists are drawn again from the answers stored in them, so the page shows what was typed rather than a blank or out-of-date box.
Checkboxes and radio buttons keep the ticks, crosses or dots the form drew for them. Flattening only comments and markup leaves the form as it was and still fillable, and flattening only the form leaves every comment editable.
What to know before you start
- A field or comment is drawn as the file says it looks; one with no appearance has nothing to draw and is removed.
- Flattening does not hide anything that is already on the page.
- Scripts, auto-run actions and attached files are removed from every flattened file.
- A password-protected PDF needs Unlock PDF, and its password, before it can be flattened.