Hope you are doing well and sorry to hear that. As described you are unable to save the PDF and getting the error 135.
Is this a behavior with a particular PDF file or with all the PDFs that you try to save. It seems like there is something wrong with the PDF when it was created. Please try to recreate the PDF from the original source file and see if that works.
Also, make sure you have the latest version of the application installed. Go to Help > Check for updates and reboot the computer.