Sometimes there is a need to combine multiple PDF files into a single document, but this feature isn’t as prevalent on Linux PDF programs. There is a simple command that can be ran to perform this task.
pdfunite 1.pdf 2.pdf new.pdf
Open a terminal from the folder where the PDF files exist. I named them 1.pdf and 2.pdf, to remember them easier. They will then be combined in a file named new.pdf.