If you are Mac user, you probably know the function that allows saving any document in PDF format. In iOS this functionality is not available. If you want to bridge the gap with the Mac platform, a new Cydia tweak “PDF Printer for Safari” can do the trick for you.
This tweak enables a PDF file printing option in Print menu of Safari on iPhone. After installing the tweak on the iPhone, just open a web page, tap the share button in the bottom bar in Safari, tap print, then tap on PDF in upper right corner and after few moments your page will be saved in PDF format. In this way the page will be saved as a PDF and can be open in iBooks or any other application that supports this file format.