PDFoo enables linking into PDF content. The concept has a simple analogy: to link to web pages we use http:// URLs. Similarly, to link to PDFs we can use pdfoo:// URLs. These PDFs reside on your computer, and PDFoo resolves the URL to figure out which PDF to open. For example, PDFoo is wired to respond to pdfoo://apphelp/ URL to open the PDFoo help document.
Creating PDFoo URLs is easy: First, open the PDF. Second, assign a prefix such as "motion5man" for 1500-page Motion 5 PDF Manual. Third, drag out links to sections inside the PDF, or copy out specific paragraphs with links back to source, or even export annotations with links back to the original PDF.