I am trying to make a pdf with textboxes that can be written in when published om web. I make the textboxes and layout in pages but who - and is it possible(?) - can I make it possible to write in the textboxes in the pdf?
Basically, PDF captures the type, but does not necessarily capture the underlying text. PDF began as just viewable PostScript, that is, PostScript page descriptions converted into a modified page description model for direct imaging on the display. So PDF as such is not editable - unlike the Pages format, the Word format, and so on and so forth.
You can create input interfaces in a PDF, which can be used in production of forms for business and government, but to create input interfaces in a PDF you need software other than Apple Pages. You would probably want to look at ways of doing what you want in HTML, unless your project must have what e.g. Adobe has to offer in the way of forms production facilities.
/hh