Make sure that the Security Tab has no check mark. · Make sure the file is saved as “Restricted PDF” or “Unlock PDF”. Download Restricted PDF. STEP 2: Open the file and sign the PDF using Adobe Sign PDF Sign or the image signing plugin. · If the Adobe Sign button doesn't appear, check the file type. If the form doesn't appear, it's likely that the PDF isn't secure. To fix this, go to File → Properties → Security and make sure that the security tab has a check mark. STEP 3: Print out the completed PDF or scan it into a photo file such as a .pdf or .png file.