Here are some simple instructions on how to combine multiple PDFs into a single PDF using Adobe Acrobat DC.
Open Acrobat Pro DC and click Tools (found on the upper left corner of the app).
Click Create PDF.
Select Multiple Files and click Next. You can now drag and drop the PDF files that you want to combine together onto the dashboard.
Click Combine to create a single PDF file. Then you can download the new file you’ve just created.