Yes, flattening PDFs is completely free on PDFA2Z.

What does flattening do?

It merges all interactive form fields, annotations, and layers into static content that cannot be edited.

Free Flatten PDF Online

Lock down your filled PDF forms by flattening them. Prevents editing of form fields and merges all annotations and layers into a single printable layer.

Upload your PDF form or layered PDF.
Click "Flatten PDF".
Download the flattened, print-ready PDF.

Is it free?: Yes, flattening PDFs is completely free on PDFA2Z.
What does flattening do?: It merges all interactive form fields, annotations, and layers into static content that cannot be edited.