Options:
I have embeded a PDF with fillable fields so the user can type in letters.

I have also a code to insert media look like this:
<iframe frameborder="1" height="200" name="frame1" scrolling="no" src="http://........../wp-content/uploads/2013/12/what1.pdf" width="550"></iframe>.

Now to the questions:
How to update or replace thus file on a page directly? is there any option to customize this?

Regards: Xiao_coffe