An original print by Pablo Picasso would be quite valuable. Original prints refer to prints made by the artist that are original in themselves, not reproductions of other artwork. Not all prints are signed. A signature increases the value. Some signatures were included on the plate as opposed to each piece being signed.
Limited edition prints refer to small runs. Look for a number in pencil that looks like a fraction at the bottom of the print. The lower number shows how many prints were made. The upper number shows where your print falls in the run. For instance, 5/100 means that a print was the fifth one made in a run of 100. Lower numbers mean higher values.
Artist's proofs are valuable as they were not made to be sold. P/P means the printer's proof.
If you believe that you have an authentic print, as opposed to a reproduction, you need to consult an art appraiser. An authentic print by Picasso would be quite valuable. Find an appraiser in your area by checking the Appraisers Association of America or the American Society of Appraisers.