Print multi-contents into a single file through an URL /print/pdf/node?ids={34,100,1000}

You might need to think about a server-side command for it (eg send these ids to the queue and queue processing will generate PDFs of those nodes) as it might take too long and browser request will timeout if your nodes are too long/big and take too long to concat.

Also, you can entity-print a view with full display of those ids.

I generate 40-50 page long documents using this module (including 10-15 different nodes) using a queue processing - no way it's possible to do in browser requests (unless it's a long running op).