Do I need to attach the letter of acceptance of an accepted paper along with the paper itself to my CV for applications to phd programs?
The typical way to list such a paper is


  'author, author, and author. "Title", Journal of XYZ, to appear'


That should be enough with regards to your C.V.  Anyone in academia will be familiar with this notion, and is unlikely to be think that you might be lying.  After all, the truth will become obvious one way or another shortly.

If they want to see copies of your papers, it's OK to attach a preprint as well, as long as you clearly label it: "Preprint, do not distribute." Many journals will in preproduction have sent you a proof copy with exactly this as a watermark.
Sharing in this way clearly falls under fair use protection, even if you have transferred copyright, just as if you were showing it to them in person.