I need to merge a lot of PDFs, and I want to to it programmatically.

From a supplier I have received a total of 525 PDFs plus a list of products and a list of which PDFs belongs to which products. The supplier thinks it is a good idea to let the client click on different PDFs for each products, because many PDFs are relevant for more than one product. However, I think this is a terrible idea, so I want to merge all the relevant PDFs for each product into only one PDF per product.

I searched for "merge PDF" here, and found some references to iSEDQuickPDF, but that product is in practice not supported anymore. I may buy it and take a chance that I can use it, but the evaluation option is not available anymore. So I either need other options or I need some "persuation" from current users of iSEDQuickPDF.