Hi Julia. I'm Greg, an installation specialist and 9 year Windows MVP, here to help you.
If the pen button will let you sign with your finger or mouse, then fine. If not you might want to install Adobe Acrobat which lets you interactively fill in forms better than built-in Edge for PDF files.
You can also print out the doument, sign it, then scan it back into the PC to attach and send back. This is what I do since signing with mouse always makes a mess for me.
I hope this helps. Feel free to ask back any questions and let us know how it goes. I will keep working with you until it's resolved.