Merge PDF Files Online

What does a PDF merge tool do?

A PDF merge tool takes two or more separate PDF files and combines them into a single document, keeping every page from every file in whatever order you choose. It's the tool to reach for when you have a contract, a cover letter, and supporting scans as separate files but need to send or file them as one — rather than attaching several files separately or using a printer-driven "print to PDF" workaround.

How to merge PDF files

Add your PDFs by dragging them onto the tool or choosing them from your device. Each file appears in the list on the left, numbered in the order it will appear in the merged document. Reorder files with the up/down arrows if needed, rotate a file's pages if one was scanned sideways, then press Merge PDFs. The final page order updates on the right as you make changes, so you can check it before downloading.

How to reorder files before merging

Every file in the list has up and down arrow buttons next to it. Clicking them moves that file earlier or later in the list, and the merged PDF's page order always matches the order shown — the first file's pages come first in the output, the second file's pages follow, and so on. There's no separate "preview" step with a different order than what you see in the list; what you see is what gets merged.

File limits and supported PDFs

Add up to 20 PDF files in a single merge, each up to 50 MB. Any standard, unencrypted PDF is supported. A password-protected PDF can't be opened by this tool without the password, so it's flagged as encrypted and left out of the merge rather than causing the whole merge to fail. A damaged or invalid PDF is flagged the same way, as unreadable.

Rotating pages

If a file was scanned sideways or upside down, use its rotate button to turn every page in that file 90 degrees; press it again to keep rotating through 180 and 270 degrees. Rotation is per file, applied to all of that file's pages at once, and is included in the merged PDF without altering the original file on your device.

Common errors and troubleshooting

• "This file isn't a PDF." Only files with a .pdf extension and PDF content are accepted; a renamed file of another type is rejected rather than silently included.
• "This PDF is password-protected." This tool can't open an encrypted PDF without its password. Remove the password in another application first, then try again.
• "This PDF couldn't be read." The file is likely damaged or incomplete. Try re-exporting or re-downloading the original PDF.
• Wrong page order in the result. The final order always matches the file list on the left — use the up/down arrows to fix it before merging, or check the "Final page order" panel on the right.
• Merge fails on a very large file. Each file has a 50 MB limit; a smaller or re-compressed copy of an oversized PDF will merge successfully.

Does SkyyCast upload my PDFs?

No. Every PDF is read and merged entirely in your browser using a client-side PDF library — the only network request this page makes is loading that library's own code, which never carries your file data. Nothing is sent to SkyyCast or any other service, no account is needed, and closing or reloading the page discards everything.

Frequently asked questions

More free tools

See all free SkyyCast tools. Need to turn images into a PDF first? The Image to PDF Converter builds a PDF from JPG, PNG or WebP images, which you can then combine here. Need a smaller file after merging? Try compressing images before converting them with the Smart Image Compressor.