[strike]Firstly, you are using double-quotes instead of single quotes. Single quotes are more appropriate.[/strike] Oops, my tired old eyes!
Secondly, you have used mixed case, lower case is more reliable.
Thirdly, there is a space in the file name "Delivery Schedule.pdf". Try renaming it "delivery_schedule.pdf" and amend the code accordingly.
Fourthly, it is very unlikely that the address "C:\Users\xxxx\Desktop\test.pdf" is accessible to your server!!! Files MUST be located on the server, or within the path of a localhost (if used).
Fifth, there is a line break between "?" and ">". That may just be an effect of copy/pasting here, but needs to be checked.