Hi Kane,
Recently updated my reply, thought it will take a while for it to reach you.
Please check this too.
Also, have your URL validated if it's redirecting to it correctly.
Try including a SITE PROPERTY such as. Site.EnvironmentURL+"/ModuleName/testpdf.aspx"
Based on your screenshot, since you are using an enterprise, have it (Write Binaries to Running Dir) as False just like my configuration.
I have a Cloud Enterprise Environment.