Merging is the best technique to combine multiple numbers of PST file into single PST file. Merging of PST file can be done by using SysInfo PST Merge software, that is simple and reliable software that can merge multiple PST file into single PST file without modifying original PST.
I am very happy for using SysInfoTools software. I have lots of PST files in Outlook and I want to combine them as per my requirement. I will happily recommended SysInfoTools PST Merge Utility.