Adobe has created a free, online tool to allow you to merge PDFs seamlessly into one document.
Navigate to https://www.adobe.com/acrobat/online/merge-pdf.html
Click “Select Files”
Select all the PDF’s you wish to combine, and hit Open
Allow for the site to process the upload
Drag the PDFs in whatever order you want
Click “Merge”, it will then show you the status of the merge
Once it says “Your merged PDF is ready” scroll through the previewed document to ensure things look as expected.
Then select “Download” and rename the PDF into whatever you’d like!