What to do if markups don’t stay on the drawing when using the Measurement tools.
You’re trying to perform length or area measurements, but the markup won’t stay on the page.
Make sure the Make Annotation box is checked at the bottom of the Measurements tab.
Check to see if Security is defined in this PDF file. The person who creates a PDF file can define Security that does not allow adding annotations or markups (including measurements) to the PDF. If you can’t check the Make Annotation and Store Scale in Page check boxes and all the markup tools are grayed out, then the Security of this PDF does not allow markups to be created.