As the title states: What is the best or cheapest library for creating PDF files in Delphi?
I think Rave Reports is included with most Delphi versions. It supports writing reports to PDF files. Since you already paid for Delphi, this would probably be the cheapest :-)
A free solution would be to create a Postscript file manually in Delphi. You can first produce your document/report or similar and save it in PS format in some vector drawing tool. The resulting file is ASCII so you can use it as a template and substitute your desired content by modifying it in your own Delphi program.
Finally, call a free PS to PDF converter on the file. For example on this page you'll find a link to such a tool (GPL GhostScript).
Best OR cheapest. These hardly ever combine well.
"Give me you biggest, strongest, cheapest drink."
-Bender Bending Rodriguez
If you need something simple then PowerPDF works well as it generates a simple PDF document. pdf in the box is also a good solution I have used in previous projects and is a native VCL solution and supports more of the PDF specification.
Report Manager is a complete reporting solution avilable under the Mozilla Public License.
It has a designer, a (optional) server and can be compiled inside your .exe by Delphi.
Gnostice have some very neat native VCL components (eDocEngine, PDFToolKit) for Delphi and C++Builder.
We Use VisageSoft, which can be used with Delphi and VS http://www.visagesoft.com/
LibHaru works fine. And is free. You have to understand pdf to use it, though. There is no real abstraction layer above it to provide paragraph and page models. Otherwise, generate LaTeX and use pdfLaTeX to create nicely formatted documents