Right now Bluebeam is the industry standard and as far as I am concerned, unmatched by anyone else and very inexpensive. About $350-$375 per seat then $99 per year for the maintenance contract per seat which includes free upgrades and support. We have 3 seats and pay just under $300 per year to maintain the license on all three. Basically a seat means a computer so as long as BB is installed on the computer, the license it attached unless you detach it from the computer.
One of the most important aspects is verifying that the PDFs submitted are digitally signed and sealed by the RDP and BB has a way to do that. Just make sure the RDP has settings that allow markups by the plans examiner.