Unless you have Adobe Acrobat Pro at your disposal it is not very straightforward to mark up PDFs that subsequently can not be easily edited, e.g. if you need to blank certain passages in a text document without rewriting the document for that specific purpose. We also found that the current version of Adobe Acrobat Pro does not create PDFs that can not be edited with Apple Preview.
One old school approach to this is to edit the PDF in Adobe Acrobat (Reader or Pro), then print and scan the document – the problem with this is that the resulting PDF might be rather large, depending on your printers scan settings.
To get this done in a more convenient way, do the following:
1. download and install PDFwriter, basically this creates a virtual PDF printer that btw. can also be used to create any size PDF;
2. edit the PDF in Adobe Acrobat (Reader or Pro), then go to the print dialogue and under the Advanced tab choose to ‘Print as Image’
3. next choose PDFwriter as your printer and print, the resulting PDF is accessible in /Users/Shared/PDFwriter/YOURUSERNAME
Although a bit of a workaround the above reliably creates PDFs which are not easily edited.