PDF Replacer ... force bold text, underline, strikethrough, and so on. 2] Next, type the text you want to replace and the text with which it should be replaced. You can add multiple text combination.

There are several applications that enable you to replace text in PDF files. Adobe PDF files can be created and read on various computer media, such as mobile devices, PCs and Macs, as well as ...

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.