how do i combine multiple pdf files into a single pdf file?
You can combine files using Adobe Acrobat in a number of ways - through the context menu when a group of files are selected in Explorer or Finder, by drag-drop onto the Acrobat icon, using the Create... button on the Acrobat toolbar and the Combine Files button on the welcome screen.
See the product help file
Recent versions of Acrobat have had such a command in the File menu. In the current version—Acrobat XI—it would be File > Create > Combine Files into a Single PDF. The wording might be slightly different in earlier versions of Acrobat.
The thread was started in early March and it's Mid-April, I know this very well. The OP of this thread posted a very common and simple question or maybe he/she would have resolved this. For an Adobe Acrobat user it's not at all difficult to combine multiple PDF files into one. But to combine PDF files full version of Adobe Acrobat is mainly required, otherwise PDF files can't be combined. For example, I'm using Adobe Acrobat 9 Pro. These simple steps are mainly required to combine PDF files:
A new PDF file will be created and all the selected PDF files are combined in it. The steps shown above might be different in other versions of Adobe Acrobat. Other than this, some third-party PDF merge software are also available. Most of them are available with a demo version for free evaluation. I've heard much about SysInfoTools PDF Merge software on other forums and directories and it's demo version is freely available. One may check its demo version if Adobe Acrobat (full version) is not available.