php edit interactive pdf form

I have an interactive pdf that has a few forms with input fields and checkboxes. I need to open this pdf with php and complete the fields. Is there a way to do that with php? If yes can anyone recommend a library, preferably free.

PS:开发者_Go百科 looked at Zend_Pdf in version 1.11. Seems it might be able to do the job but no documentation is there about this.

Thanks

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I use http://www.setasign.de/products/pdf-php-solutions/setapdf-formfiller/ in my projects. Works very fine but not freeware