The tools we are using to add a text box to a PDF document in this post are: Foxit PDF Reader iLovePDF. Let’s check both of these tools. 1] Foxit PDF Reader ...

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.

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.