With Adobe InDesign, you can align text horizontally as well as vertically within a text frame on the page. Aligning text horizontally gives you the ability to justify the text to the left, center ...

Microsoft Edge provides a feature to highlight text in PDF and save highlighted PDF to your PC. This post shows you how to to highlight and save PDF using Edge.

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.