Did you know?

There may be a time that you want to add comments to PDF file that you are handing out, but you do not want to change the original file. To add comments to your PDF file or markup you PDF documents in Mac OS X, you will need to download a PDF editor to begin making annotations to the PDF file
Add new annotations, use the text highlighter when underlining main ideas or important information, and markup PDF files from any device. And when you edit and add notes to a PDF page, changes are automatically saved to your Dropbox, and you can easily share the annotated text with your co-workers
You can add comments to any PDF file, unless security has been applied to the document to prohibit commenting. In most cases, you’ll use the commenting features to provide feedback to a document’s author, but you may also find them useful to write notes to yourself as you’re reading documents