Troubleshoot merge failures by checking encryption, damaged files, file-size limits and the total number of pages before retrying with a smaller set.
Check whether every source opens normally
Open each PDF in your usual viewer before selecting it for merging. A file that fails there may be incomplete or damaged. Download a fresh copy from its original source when you have access, rather than repeatedly retrying the same broken file.
A filename ending in .pdf does not prove that the content is a valid PDF. Renaming another type of file does not convert it. Use the original application's export function when you need a genuine PDF copy.
Recognize unsupported encryption
ToolNivo rejects encrypted and password-protected PDFs. It does not provide a password entry field or a decryption workflow. If you are authorized to use the document, obtain or export an unencrypted copy through a suitable application before merging.
A source may be encrypted even if your viewer opens it without an obvious password prompt. Do not assume a parsing error means the website has lost your file; the tool may be refusing an unsupported protection mechanism.
Review the selection limits
Each selected file must be no larger than 30 MB. The combined selection is limited to 100 MB, 20 files and 500 pages. If some files are accepted while others show errors, compare the list with your intended set before continuing.
A device may still run short of memory below these limits. Try a smaller group to identify whether one document or the total workload is responsible. Keep the tab open during processing and save a successful result before clearing the selection.
Check the output after a successful retry
When merging succeeds, verify the page count and source order. A retry with fewer files can produce a valid PDF that is nevertheless incomplete for your original purpose. Do not send it until you have confirmed that every intended section is present. Preserve the separate originals so you can reconstruct the final document if another conversion is needed.