Based on https://ironpdf.com/examples/merge-pdfs/
IronPDF offers the capability to amalgamate the contents of various PDF files. This function is especially useful for adding cover pages to new or existing PDFs. It also facilitates the consolidation of pertinent documents into a single file, which simplifies both printing and distribution.
In the provided code sample, the PdfDocument.merge method is applied to two PdfDocument instances, both generated from HTML content. The outcome is a newly created PdfDocument in which the contents of the second PdfDocument are affixed to the conclusion of the first.
For merging more than three PDF documents, initiate by forming a list that encompasses the necessary PdfDocument objects. Subsequently, submit this list to the PdfDocument.merge method as a singular argument: