If you ever need to edit a PDF, you can try to convert it to a word doc or use a PDF editor.
I would suggest using a free PDF editor- you can find this by searching in Google "PDF editor" and a huge list will come up.
Click on any one of these- the following will be the same rules for pretty much any site you use. Below is an example from https://smallpdf.com/edit-pdf
Upload your PDF document.
In this case, you'll click "Choose files" and then click on the file you wish to upload.
Edit it using the site provided tools.
You'll see that this one has a pencil tool for a signature, a text one to type out things, and a highlighter to highlight. Most online editors will have these same tools.
Download the finished document.
When you are done editing the document, click "Download"
That's it!
https://www.sejda.com/pdf-editor is another great site