The second most common question we get about DITA-based systems is “How do we publish nice-looking PDFs?” (First, by far, is “How do we migrate our content into DITA?”)
DITA Open Toolkit
First up is the DITA Open Toolkit (DITA-OT). The DITA-OT is the first possibility most people encounter as they move content into DITA and start looking for PDF output. But the default output from the DITA-OT is astoundingly unattractive, which led to DITA having a reputation for producing terrible PDF.
Configuration requires an understanding of the DITA Open Toolkit, along with XSLT and XSL-FO. It is not for the faint of heart.