This pdf is 39 pages long, 1 page front cover, 1 page editorial, 1 page ToC, 1 page containing both SRD and Index. That leaves 35 pages of content.
Incantations kicks off with an introduction to the spirit world, explaining how spirit magic and incantations are neither truly divine nor arcane, how they represent a primal power that can be tapped via rituals by anyone who knows how to do so, but may exact a price. (2 pages)
The first chapter describes Incantations from the general area of Vodou. It introduces the concepts of rado, petro and guede Loa which are not bluntly described as the traditional alignments but rather differences in the temperament of the more or less amoral Loa. We get 7 Rada Loa, 5 Petro Loa and 8 Guede Loa in this chapter. Apart from several nice incantations we also get a new disease in this chapter. My favorite incantation makes it possible to literally shed ones skin and temporarily become a incorporeal form, including attacks etc. (12 pages)

The second chapter details the so-called Middle World, inspired by Slavic mythology. We get 6 spirits and a sidebox with two great ideas spawned from mythology about spirits and 8 incantations. They have a completely different feeling from the first chapter and make EXCELLENT additions to e.g. a "Tales of the Old Margreve" or otherwise Slavic-inspired setting.(12 pages)

The final chapter details the Arcanum and its utterly alien, slightly Lovecraftian patrons from beyond the stars and contains 4 quite complex incantations as well as a sample lodge and 5 sample patrons.(9 pages)

Conclusion:
Editing and formatting are top-notch, the pdf comes in full color and is a beauty to behold, complete with nice artwork and its own distinct style. However, it will test the mettle of your printer and a printer-friendly version would have been very much appreciated. With regards to the content, I can only say: WOW. I've always somehow disliked the fact that magic has become a more or less predictable commodity in RPGs and, while I always understood the necessity of predictable systems, this little file adds one stable of fantasy literature and mythology I always missed: The powerful, cool rituals and negotiations with other entities, the underdog non-caster somehow cursing his opponent. The wise woman beseeching the spirits of nature etc. - without being druids, mages etc., has too long been absent from our favorite systems and these incantations are not only expertly written, make great hooks for adventures and put the awe and unpredictability back into magic, they are also plain fun, creepy and/or cool to read. If this pdf does not inspire you to write an adventure, I don't know what will. The system is elegant, concise and should be included in the standard PFRPG-canon. My only two gripes are: I want a sequel, a whole book of incantations and I want a printer-friendly version. Content-wise, this is a straight 5-star-file, but be aware of the lack of a printer-friendly version. If that's a problem for you, subtract a star. My final verdict will be 4.5 stars, rounded up to 5.