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.

You can type on a PDF using one of several different options depending on the device you're using. All of the programs listed in this article are available for free, and some methods are built ...

To add your signature to another spot or a subsequent PDF, click on the Sign icon and choose your saved signature. After you’ve added text and signed the PDF, save the file.