Highlighting/Underlining pdf

With some pdfs, the toolbar for highlighting, underlining,etc., is greyed out. I can open it in Preview or Highlighter and do that, but not in DTPro. The Info panel says it is pdf + text.

Please explain.

This has been discussed many times on the forums.

  • Some PDFs are encrypted and don’t allow editing.
  • Some PDFs have fonts that are incompatible with Apple’s PDFKit framework available to us. Preview uses features unavailable to us in their framework. Other applications don’t use PDFKit.