📋 Interleave Rules:
▪ Take page 1 from file 1 → page 1 from file 2 → page 1 from file 3 ... then page 2 from file 1, loop until all pages are used.
▪ If a file runs out of pages, it will be skipped and pages will continue to be taken from remaining files.
▪ The final PDF page size will follow the first page of the first file.