Writing in Adobe after sending it in an email

I am working on a document and sent it through an email to others. Afterwards, when I opened it, I haven't been able to edit the document in any way. It is a premade document that I filled in partially, but now I am unable to change anything I wrote or write in it further. I've tried making copies of the document and opening it multiple ways. I've previously had problems changing, deleting, and adding numbers into a premade chart after clicking out of the box. What can I do to make the edits work?

Thank you!