Merge PDF joins files in the order you choose and downloads one PDF. Use it when a form, a letter, and a scan need to be a single attachment.
Image files are not PDFs. Turn those into a PDF first with Images to PDF, then merge.
Questions
Can I choose the page order?
Yes. Drop the files and arrange them before you download the combined PDF.
Is there an upload step?
No. Merging runs with pdf-lib in this browser.