1. I upgraded to the PRO version, paid for it, but I don't know where to enter the key I received with my invoice.

In the same email that had your key you should have a download link to the PRO version. Install that build and you will be prompted to enter your upgrade key. If for some reason you can't find the download link, please contact us and we will send it to you ASAP.

2. I get an error message when I try to merge more than 5 PDF files.

You cannot merge more than 5 PDFs using Adolix Split and Merge PDF. If you want to merge more documents, feel free to upgrade to Adolix Split and Merge PDF PRO.

3. I get an error message asking for password when I try to merge/split PDF.

You are asked for password because that PDF is encrypted. After you enter the password, retry the split / merge process.

4. How to use command line arguments?

It's easy. Just follow the syntax described below. Use full path for all files.

Command line arguments with output file selected by GUI (program opens)

a) for splitting: -s filename or -s "filename", where filename is the PDF you want to split.
AdolixSplitandMergePDF.exe -s C:\temp\report.pdf

b) for merging: -m "filename1" filename2 "filename3" , where each "filename" is a file you want to merge. AdolixSplitandMergePDF.exe -m C:\temp\FileA.pdf C:\temp\FileB.pdf C:\temp\FileC.pdf

Command line arguments with output file selected by command line (program does not open - 100% quiet)

a) for splitting: -qs filename or -qs "filename", where filename is the PDF you want to split.
AdolixSplitandMergePDF.exe -qs C:\temp\report.pdf

b) for merging: -qm "filename1" filename2 "filename3" -o "outputpdf", where each "filename" is a file you want to merge and "outputpdf" (with or without "") is the output file. AdolixSplitandMergePDF.exe -qm C:\temp\FileA.pdf C:\temp\FileB.pdf -o C:\temp\merged.pdf

5. You claim to have multi-language support, but I can't change the user interface to my language.

Help us translate our user interface to your language. Have a look at Adolix Split Merge PDF translation page.

6. Why should I use your product and not an online split & merge PDF tool?

Adolix Split and Merge PDF processes your files locally on your computer — your documents never leave your machine. Online tools require uploading sensitive PDFs to third-party servers, raising serious privacy concerns. Adolix also works offline, has no file size restrictions, and is faster since no upload or download is needed. Read our full comparison for more details.