PDF/X-4, Colour-managed, CMYK, gray, RGB or spot colour data are supported, as are PDF transparency and optional content. A second conformance level named PDF/X-4p may be used when the ICC Profile in the output intent is externally supplied.

If you want to create a fillable form field in an existing pdf file, you may can a pdf editor. Or if you have acobat x/pro, you can turn to it.

If you want to make your existing PDF file editaable you could still use PDF Editor. With it you can edit the pdf directly.

Mac OS X has PDF creation built in. Select Print and then select PDF from the Print dialogue window and select an apposite option.

Here are two most popular software to view PDF in Windows:

1. Adobe Reader

2. Foxit Reader

and two most popular applications in Mac OS X:

1. Adobe Reader

2. Preview

May these help you.

Mac OS X has PDF capabilities built in so any application running on a Mac, including iWorks, can save as a PDF from the Print dialogue box.