This PDF file contains a copy of the first four volumes of the Philokalia, which are the only four translated into English (only the fifth remains to be translated). The Philokalia is a collection of texts from many saints throughout the centuries dealing with the spiritual life in general and prayer in particular. It is often considered to be the definitive collection of works on prayer and remains one of the most popular collections in Orthodox Christianity. Still, its depth requires guidance: if you are interested in reading the Philokalia, I would especially encourage you to do so with help from an Orthodox Christian who is experienced in these matters. My immediate reason for having the PDF version of the Philokalia was a book group I participated in in 2009, where the digital copy made much more sense to use. More generally, I keep this because it is an invaluable resource: it contains writings from Fathers of the Church which are otherwise in diverse locations or unavailable in English.
The Philokalia itself was compiled by Ss. Nicodemus (or Nikodimos) of Mount Athos and Macarius (or Makarios) of Corinth in the 18th century; it is in the public domain. The English translation of the Philokalia was undertaken by G.E.H. Palmer, Phillip Sherrard, and Bp. Kallistos Ware; it is published by Faber & Faber and presumably under copyright. I am not sure who the author of the PDF version is, or its copyright/left status..
I created this metadata on September 25, 2011 and last modified it on August 23, 2013.
1. I don't think this is where I originally got my copy from, but the file here is identical to mine as far as I can tell.
2. This is the number of physical pages. The pages in this file are improperly sized: the visual pages are larger than the physical page size, causing them to take up slightly more than one physical page. This makes the file very unsightly to use, but still functional.