What is the difference between lowagie and iText? Is this just version difference or an upgrade to the library. Which one is recommended to be used?
I am Lowagie, the lowagie you refer to. This is what I have to say about this: http://itextpdf.com/salesfaq
You should use the latest version of iText. Currently that's iText 5.3.4.
I'm the original author of iText and the author of the "iText in Action" books.
The differences between old versions of iText (iText 2.x.y dates from July 2009 or earlier) and newer versions of iText can be found in the changelogs: http://itextpdf.com/changelog
The 5.0.0 version had the following substantial changes:
com.lowagie to com.itextpdf.Numerous bugs have been fixed since July 2009. Functionality that makes your PDFs future-proof such as updates regarding new digital signature standards and new standards such as PDF/UA, PDF/A-2 and PDF/A-3 is only available in the more recent iText versions.