This post helps to add a text box to PDF using a free software and an online tool. You can adjust the size of text box, text style, etc.

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.

In other words, Adobe Reader won't let you add text. What you need is a program that's a little more accommodating, PDF-wise. Try Foxit Reader 4.3, which allows you to add text to any PDF.

EaseUS PDF Editor offers a complete set of PDF-editing tools to add edits to PDF files on your Mac quickly and easily, and it even converts scanned documents to text. Edit texts with format ...

Need to edit a PDF document but don’t want to pay for the more expensive Adobe editors? You can add text to and sign a PDF with just the free Reader program.

Gimp is normally used to create or manipulate images files, but can also work with PDFs if you understand how it works and what it's limits are.