I was recently dealing with needing to fill in a PDF form and then supply it to someone as a flattened PDF so that they couldn’t (easily) edit it. I don’t know what the creator of this PDF did however not only did this PDF not open in Preview, but even when it was opened in Acrobat, you could only see the parts of the PDF you were able to fill out. It wasn’t until it was printed that all the extra terms and conditions were also visible.

It can be very difficult to flatten a fillable PDF form from Acrobat on macOS – Adobe Acrobat Pro doesn’t let you save it as a flattened format as it contains XML form data and Adobe no longer add a PDF Printer to macOS when you install Acrobat.

Furthermore, Acrobat specifically blocks you from using the built-in print to PDF functionality that works in just about every other app on macOS, telling you instead to go to File > Save As. This however does not save a flattened PDF, but rather just saves the editable PDF form.

As it turns out however, Rodney I. Yager over on GitHub has created the RWTS PDFwriter

This simple app installs a PDF Writer printer, that you can then use from within Adobe Acrobat Pro to print a flattened PDF.

By installing Rodney’s app and printing to the PDF Writer printer, this saved out a properly flattened PDF with all of the required information visible in the file.