Wrong Format? Merge with IlovePDF

Hi everyone! I am trying to create automatic Proposals from my Notion and save it as a PDF in my Google Drive. I have reached the part where I could create them and save them easily, but now I wanted to merge three pdfs together (There are two PDFs that were designed to give more information to the client, and the one I have just created with Notion). The problem is that the module of IlovePDF is saying that my file are in wrong format, I am new in this so I tried to use the Array Aggregator function without luck.