Use a PDF editor or merger tool
Open the first PDF
Choose the option to add or append another PDF
Select the second PDF
Arrange the order if needed
Save the combined file as a new PDF
Use command-line tools like `pdfunite`, `pdftk`, or `qpdf` if preferred
Use programming libraries such as PyPDF2, pikepdf, or PDFBox for automation
Verify the merged PDF opens correctly and pages are in the right order