Are you trying to do this with code, or within HTML? Is this on a local network path, or are you trying to save it somewhere from an external site?
If you've put the PDFs where they belong (assuming network) and you want the user to be able to open it by clicking on a webpage link, write your tag out with something like:
<embed src="D:\Thepath\ToYour\File.pdf width="600" height="700" type='application/pdf'> Web page Text here for your PDF </embed>
Also, it shouldn't be necessary to double-up on the backslashes, as HTML doesn't use escape characters this way (UNLESS it's actually happening in code from somewhere).
It may be worth looking into some of the responses from this article here, about whether to use an embed or object tag: Recommended way to embed a PDF in HTML