thank you, this save as method circumvented the encryption, another hoop to jump through but whatever.
I'm also using this to do my book keeping for taxes, and want to annotate my digital bank statements instead of printing out reams of paper to markup physically.
Thanks to y'all for hashing out a soluttion that could be easily googled.
oh for anyone wondering my workaround/workflow on OSX Catalina was open the statement pdf in Preview and then:
File > Export as PDF... and the resulting file will be editable/saveable
(because at some point I have spent hours marking up a pdf only to realise my marks would not be saved, and there was much gnashing of teeth and renting of garments and wailing)