Hi @Blerion_Muco, I am afraid my knowledge of the PDF format has not changed since this topic first came up. Since n8n doesn’t have a built-in operation for merging multiple PDF files into one I suggest you use an external service for this.
I know the folks from Cloud Convert built a community node that supports such an operation, though I haven’t tested it first hand yet. Could be worth a try though, you can find the node here:
To convert base64 data into an actual binary file (and back) you can use the Move Binary Data node as shown here.