What is the meaning of Pp?

pianissimo

per procurationem - Latin for by agency or by proxy - used on a letter to indicate that has been signed on somebody else's behalf.

plural of p; abbreviation of pages.

Initialism of percentage point.

Initialism of past participle.

proton and proton (used attributively to describe a collision or other interaction of these two particles)

Eye dialect spelling of pee-pee.

Abbreviation of perempuan (“female; woman”)

Source: wiktionary.org