Sorry for being late here.
If you are having Adobe Acrobat (full version) installed in your system, you can merge any number of .pdf files into one. I'm using Adobe Acrobat (XI) and do such thing by using these steps:
- Launch Adobe Acrobat tool.
- Click on Add Files and select all the .pdf files from your system which you want to combine into a single file.
- All the selected .pdf files are shown in a list on your screen. You can also reorder the files in the list. You can also remove the file from the list if it is selected mistakenly.
- Once you are finished arranging the files in an order, click on Combine Files.
- Now click on File tab > Save as > PDF.
- Type a new name and click on Save to save this new file.
Or if you do not have Adobe Acrobat full verison, you are not be able to perform the process of combining .pdf files by using these steps. In such situation you need to go a third-party software.
I suggest you to Google.