We secure our PDFs so that the document can not be changed or printed.
We are using Acrobat Pro DC and distill the postscript file using the distiller.
Specifically we set the restrictions as
Printing = Not Allowed, Changes Allowed Any except extracting pages.
Enable text access for screen reader devices for the visually impaired is checked.
Change permissions is password protected.
Options for Compatibility Acrobat 7.0 and later
Encrypt all document contents except meta data.
The problem is that the our writers making PDFs in another location and our internal customers cannot search the secured PDFs. The people in our location can. Even the files that they cannot search, we can.
Search behavior is as follows. Search either stops after finding the firsts instance of the word, or search will not find any instance of the word past the first page.