Enlarging a PDF document attached to a Visio page

[Jmichea]

I am attempting to insert a PDF document to a page in Visio 2013. It inserts fine but when I try to enlarge the PDF in Visio, the PDF becomes unusable appearing almost bitmapped and pixilated. I don't recall this happening in previous versions. 

Please help as I need to add a layer to add points to a PDF diagram and the tools on Acrobat Pro will not suffice.

[JuneTheSecond]

Though it is not complete solution, but better a little.
If you have Adobe Acrobat XI Pro,
save your pdf file as Microsoft Word document or Powerpoint Presentation,
and insert saved docx or pptx file into Visio.