There many out there that you can try. However, most free and open-source stuff requires a bit of work compared to paid ones.
Here are a few tools that that I used before:
wkhtmltopdf[
^] - Free and it works
Iron[
^] - Paid and easy to integrate and use
Aspose PPDF[
^] - Paid
Other paid tools:
* abcpdf
* pdftron
The bottom line is, if you want less/minimal development efforts to integrate PDF generation, then you should consider buying a commercial one.