Are you seeing a (e.g., "Page cannot be displayed")? Are you trying to embed audio directly into the PDF? What device are you using to study (Laptop, iPad, Kindle)?

Use a PDF editor (like PDF-XChange Editor or Preview on Mac) to insert bookmarks .

: Upload your file to an automated repair service like ILovePDF Repair or Sejda PDF Repair . These engines rebuild damaged cross-reference tables instantly.

: The material is often split into thematic parts, such as: