Infix PDF Editor is just great :)

I prepare academic papers quite often so have to work with lot's of pdf documents. Usually after reading more than 15 papers its hard to keep track of every document you read. I was looking for a software that would allow to edit, especially comment, pdf files for free or other good licence.

I found Infix PDF Editor
http://www.iceni.com/infix.htm

It's suprisingly fast! I tested it on 300 pages files and it works great. After making some changes, Infix adds only small watermark at the corner of 1 in every 10 pages or something like that. It's very simple to use, quite intiutive, but still gives you everything you need.
Nice addition is also PDF printer however I'm used to pdf995 so I'm not sure if I will change the printer :) You know it's always better to have less programs but with more functions that one programe to one task :P So maybe I will use Infix printer.

It is the best software I found in this area. Maybe you have other suggestions. I recommend trying Infix :)

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Polish: Infix - naprawdę dobry edytor PDF. Trialowa wersja działa bez problemu i jedyne co robi to dodaje co 10 stronę malutki znak wodny w rogu kartki. Z tego co zdążyłem sprawdzić działa bez limitu funkcji i bez limitu czasu więc warto zainstalować. Bardzo dobry edytor pdf.