Smallpdf.com – the first good PDF Merge tool online
Smallpdf’s Merge PDF is an online tool that you can easily use in your browser and provides an easy way to combine several files into one.
While there are a few other tools that perform similar tasks, Smallpdf is the first one that offers a free service without any limits on file size or amounts of documents to be combined.

Also, it is the first online tool that is feeling just like a desktop software because of its preview function.
As soon as you drop your PDFs in the app, a preview of your files will be displayed and you can switch the order of your files by drag-and-drop easily.
Besides the function to combine whole documents, you are able to switch to the “Page Mode“ of the app to change the order of single pages, delete certain pages replace one page with another of a new document.
The app supports all modern browsers and systems and does not require and installation. If there any concerns about security, the site explains its privacy policy at the bottom of the page.
Have a look and also check out the other apps on the site for PDF compression and PDF conversion to other file formats.
Website: http://merge. smallpdf.com/