I've been putting off a necessary bit of work for a long time. I had to join two PDF files (Portable Document Format files) into one so that I could send the result to a book printing service. The problem is that so many ways are suggested, and not all of them work. This morning, I buckled down to the job, and the first two didn't work.
The third, however, worked like a charm.
I copied the files to be merged to the computer Desktop.
I gave them nice simple names (LPI1.pdf and LPI2.pdf), since I'd be typing them soon.
I opened the Terminal program and switched my directory to the Desktop (cd ~/Directory)
I installed a program called Poppler (sudo apt-get install python-poppler)
I then used one of the commands in the Poppler program, pdfunite. (pdfunite LPI1.pdf LPI2.pdf mergedfile.PDF)
Done. The merged file is no larger than it should be and it looks fine.
Oh, and the operating system I'm using is Ubuntu Linux 16.04 LTS.