Glad to see this site, Thanks guys for being active. :)
Add->Existing Item on your Project.
Then add the PDF File to your Project.
Afterwards you have to set the Properties of the newly added file to the following:
Now the file will be added to your "Output" Directory after you build your Project.
Now use your
Process.Start("MyPDF.pdf") call. It will open up, as it resides in the same directory.