Adding text fields and other form elements to create editable PDF forms in Adobe Acrobat Professional XI is a straightforward process. These elements create an interactive document that is ...

Adobe describes an alternative approach to changing the font size in a PDF that works on Acrobat 2017, 2020 and DC. It changes the default font for "Add Text" and general text editing features.

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.

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.

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.

macOS added an option to try to identify fields in a PDF form so you can easily enter text or check boxes.