If you have multiple PDF files stored in OneDrive that you’d like to have merged into a single PDF file, you don’t have to look for third party software to make that happen. You can do it with the Merge function in OneDrive on the web. Here’s how that works…
In this example, I have a PDF file titled PowerShell And Microsoft 365.pdf, and I want to merge it with another PDF file. I click on the Merge PDF pages into a new PDF icon:

OneDrive then shows me other PDF files I have that I can select to have merged with the initial file I had open. Once I select the additional PDF files and verify them in the right-side panel, I click on Next:

It gives me a new file with the name of the original starting file and “Merged from” appended to the front of the name. I can then save it:

Here’s my new file, and I still am able to get back to the original files as it doesn’t change the original… it just creates a new one:
