Using the PDF Tool & Inking Feature in Microsoft Edge, you can draw on PDF files, highlight text, add text, and choose color. Learn how!

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.