If you have a Mac, you already have what you need in an app called ‘Preview’. You can open two PDFs side by side and drag and drop pages into the thumbnail sidebar. You can multi-select pages to do it quickly. If you are on a Windows PC, I don’t believe the capability exists by default so you need to install software. You cannot do it with Pdf Merging Online Reader. If you have Pdf Merging Online Pdf Merging Online , you can very quickly merge PDFs from Explorer by selecting the files and right-clicking, then selecting ‘Merge Files’. You can also just open one file and use the menus within Pdf Merging Online to do the merge. You didn’t ask how to do this for free so I assume you don’t mind paying for the software. Pdf Merging Online Pro costs $15/mo. If you are looking for something free, there are lots of online products that are free for a trial period, so if you are looking to do this for a quick job and you won’t need to again in the foreseeable future, try out something like PDFfiller or SodaPDF or one of a hundred different ones. Some of the available products are web apps where you upload your files and the merge happens in the cloud. If you are comfortable with sending your file to some unknown website, go for it. There are also some products that cost money but are less than Pdf Merging Online ’s price and there are some that have a one-time price instead of an annual subscription. You didn’t mention what OS you are using so it’s hard to give you the best advice. I hope this helps.
If you have anything to add, or the answer to a question you'd like answered, please feel free to comment below and share your experiences with other users. I want you to know that I really like the app, and it worked exactly as I thought it would. But I am not the biggest fan of the PDF file merging or merging apps online. They are often unreliable, slow, and have horrible interface, but if you are doing this type of work on a computer every day, you probably can’t afford anything else, so that's where I am placing my time and energy. And I hope you don’t feel the need to take my word for it.