A unit at my work has a frequent need to create large appendices of articles. The articles are usually PDFs, but might be added from a web page as well. We are a nonprofit and the specific use is helping immigrants apply for asylum. The list of articles is mixed and matched for each use, depending on the conditions that they are fleeing. Typically the final appendix is about 1000 pages long. I'd like to build a tool for them to search the list of articles, select the ones that they want, and then combine the articles into a single PDF and build a table of contents for the combined list. They also need to be able to upload and remove obsolete articles easily on their own.
SharePoint Online, possibly with Microsoft Flow and Microsoft PowerApps, seems like a nice interface for this task. I.e., easy to upload and tag the documents for later search and retrieval. But I can't figure out if there is a way to combine the PDFs into one file without a large subscription fee.
I am aware of Muhimbi but our PDFs would probably be larger than 25 MB and so the pricing is too high at $500/month. I'd also like to be able to share this solution with other nonprofits doing immigration work, and a cost makes it less likely to be used.
I'm new to programming SharePoint and to Microsoft Flow. I am very familiar with open source PDF tools for Linux and I know I can merge PDF files on the Linux commandline, and I could make a PHP or Node backend for this. Can I connect Flow to an arbitrary API, maybe using the Azure integration? Is there any other low-cost solution for merging PDFs with SharePoint online?
The output does not actually need to be a PDF, but I do want to preserve page fidelity so the table of contents remains accurate.