If merge, split, or compress cannot open a file, the PDF is often password-protected or permission-restricted. Browser tools are not the same as a desktop reader.
Common causes
Open password: without the right password, the page cannot read the content, so later steps fail.
Permissions: some files display but block printing or editing. Browser tools may hit the same wall even if you can flip pages in a reader.
Broken or unusual encryption: some scanner exports use schemes web libraries do not support.
What you can do
On a computer you trust, open the file in an approved reader, export an unlocked copy, then merge, split, or compress that copy.
If a teacher, coworker, or client gave you the password, do not leave the unlocked copy in a shared Downloads folder. Store it the way they asked.
If the real problem is size and the file is not encrypted, try PDF Compress, or PDF Split to keep only the pages you need.
Limits on this site
We do not help crack someone else’s encryption. Ask the person who sent the file for the password.
Unlocked PDFs can be merged, split, or compressed in your local browser and are not uploaded to our servers. Unlock encrypted files in a trusted environment first, then process the copy here.