The process to add a border to text in GIMP consists of the following ... JPG, WebP, GIF, BMP, PDF, and many more.

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.

PDF files have the option ... Click, or click and drag, on your document to add a box with a colored border, and type your observations in it. Choose the Text Callout tool from the Drawing Markups ...

You can choose graphic editing options such as cropping, adding a border ... Shapes can be added to a PDF using the Design tab, for example, and you can highlight text and freehand draw in ...