I had the problem of not being able to use online tools for merging PDFs. On top of that, you have no idea what these online tools do with your data.
So I decided to develop my own PDFMerger that solves exactly this problem for me.
The program is written in Python, runs on the commandline and offers an user interface.
Move the PDFs you want to merge into a folder.
Copy the path to the PDFs (all the PDFs you want to merge must be in one folder).
Start the program and follow the instructions and annotations that the program gives.
git clone https://github.com/Magii27/cl_pdfmerger.git
pip install -r requirements.txt