PDFLIB works very nicely, but it is not a report generator. It is a set of routines for building a PDF file directly. In other words, instead of creating an AFP document first and then converting it to PDF (which limits you to the "lowest common denominator" of the two technologies) you can call the routines in PDFLIB to generate a PDF natively with all the features that PDF can support.
PDFLIB runs on just about any platform, including IBM i, and is very efficient and powerful. There is definitely a learning curve to using it, though... much like calling APIs. PDFLIB is commercial software.
There is a Java package called iText that is similar to PDFLIB, but is open source. I don't like iText as much as PDFLIB, it is slower and clumsier to work with, but it is free.
Both of these options are NOT report generators, though. They're just sets of routines for making PDFs that you can call from your IBM i application (such as RPG) to generate PDFs. If you find AFP to be tedious and time consuming, I doubt that PDFLIB (or iText) would be any better. In fact, I suspect you'd find these tools to be worse in that respect.
For a report generator, off the top of my head, I know of New Generation Software (NGS)
http://www.ngsi.com/company/index.html and also DB2 Web Query (I don't have a link for it -- I found it to be slow and a bit clumsy when I tried it years ago). Both are commercial tools. I do not know of an open source report generation software.
Profound UI integrates the same way with any PDF or report generator tool. It gives you an API that you can use to open a report from the browser, and an exit program where you can call the code to generate the report/pdf/whatever for it to download.