How to import a PDF file as a template in Mail Merge

How to import a PDF file as a template in Mail Merge

Hello,

I am trying to import a PDF file as a template and it does not permit me to do so. It's a fillable form. I converted it into a .docx file using Zoho Writer  and when I tried to import it, the formatting went for a toss. Can one of you please suggest a solution to this? Thanks in advance . I am attaching a couple of screenshots of the issue.