This post helps to add a text box to PDF using a free software and an online tool. You can adjust the size of text box, text style, etc.

Devon Delfino/Insider 3. Navigate to the page you want to add text to, and then select the Text icon (it looks like a "T" inside of a rectangle). A text box will then appear on the page.

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.

Need to edit a PDF document but don’t want to pay for the more expensive Adobe editors? You can add text to and sign a PDF with just the free Reader program.

Removing text from a PDF isn't as easy as drawing a black bar across it. Fortunately, redaction tools let you truly erase sensitive text in Preview, Adobe Acrobat DC Pro, and PDFPen.