Import PDF Feature: Protect Your Drawings and Time Stamp
Issue
You're concerned that the Import PDF feature will allow others to forge your work – for example, copying your time stamp to create the illusion that you've made changes to a drawing.
Solution
First of all, theft and forgery of these items really shouldn't be a concern. The legal and professional repercussions of using someone else's drawings and time stamps are prohibitively severe.
However, if you're worried that someone might misappropriate your work, you can use Adobe Acrobat to save the file to an image and then save it as a PDF again. The image will be saved as a raster PDF, rather than a vector PDF. A raster image comprises individual pixels, making it more difficult to copy into a CAD platform to make changes or continue work.