Can I truncate multiple large PST files?

There are many tools to truncate multiple PST files into small parts but I would suggest the 100% safe tool is KDETools PST Splitter.

Features: 

• Split by date.
• Split by size.
• Split by year.
• Split by folder.
• It supports without installing MS-Outlook.
• This tool easily supports Windows and Outlook Version.
• A message filtration option is also available.

More info: http://www.merge-pst.com/manage-large-pst.html