If you are unable to select or highlight specific text in a PDF document in Adobe Acrobat Reader on Windows, this post will help you fix it.

If you want to extract highlighted text from PDF file as a plain text file, then this post covers some good free PDF Highlight Extractor software to do that.

Removing text from a PDF isn't as easy as drawing a black bar across it. Fortunately, redaction tools let you truly erase sensitive text in Preview, Adobe Acrobat DC Pro, and PDFPen.

ReaddleDocs’s PDF viewer now lets you highlight text inside PDF files in several colors, make notes at any place in the document, and save these changes in a desktop-compatible PDF format.

Apple makes adding comments, highlighting text, and adding a signature easy in macOS. Here's how to annotate a variety of files, from JPGs to PDFs, using macOS' integrated Preview.