PURPOSE How to add notes, highlights, callouts, or review comments to a PDF. GENERAL STEPS Open the PDF in an approved PDF application such as PhantomPDF, Foxit PDF Editor, Adobe Acrobat, PDF-XChange, or another supported PDF tool. VERIFY RESULTS Review the final PDF for page order, readability, formatting, signatures, comments, redactions, file size, permissions, and any hidden information before sharing. TROUBLESHOOTING If the PDF tool behaves unexpectedly, save a copy of the file, restart the application, test with another PDF, and confirm the file is not locked, corrupted, or read-only. BEST PRACTICE Keep an original copy before editing PDFs. Some PDF changes are difficult or impossible to reverse after saving.