merge documents

I am merging multiple PDFs together into one PDF and I need to build bookmarks for the final PDF. For example, I have three PDFs: doc1.pdf, doc2.pdf and doc3.pdf, doc1 and doc2 belong to Group1, doc3 belongs to Group2. I need to merge them and have to build nested bookmarks for the resulting PDFs.
A series of examples that allow you to create reports using forms. These examples were used to answer questions such as: How to merge forms from different files into one PDF? How to merge documents correctly?
I need to create a TOC (not bookmarks) at the beginning of this document with clickable links to the first pages of each of the source PDFs.
I have two PDF files, each one in a ByteArrayOutputStream . I want to merge the two PDFs, and I want to use iText, but I don't understand how to do this because it seems that I need an InputStream (and I only have ByteArrayOutputStream s).
Many people search online for examples that show them how to merge / concatenate / assemble / join existing PDF document. Instead of reading the official documentation they end up using examples that are completely wrong. In this question, you'll see how NOT to merge documents ; in the answer, you'll discover how to merge documents correctly.
I am merging different PDF documents and I would like to add a link to an existing PDF that jumps to a coordinate on another page.
I create different PDFs and then concatenate them into a single PDF. My resulting PDF is a lot bigger than I had expected in file size. As it turns out, my PDF has a ton of duplicate fonts, and this is the reason why it's so big. I would like to create PDFs which only embed font information, not the full font.