Use the Gmail Email Backup Tool is the top notch solution for Gmail backup to a hard drive. This tool backup your Gmail mailbox in various formats such as PST, OST, MBOX, EML, EMLX, MSG, CSV, HTML, MHTML, etc. 

Furthermore, it also offers to convert your Gmail emails to several email clients like AOL, Gmail, Yahoo Mail, Office 365, Thunderbird, Opera Mail, Live Exchange, Hotmail, iCloud, etc.

In addition to this, you have the option to neatly organize PDF attachments by saving them in a separate folder for easy access.

They easily supports with both Windows and Mac operating systems. To get a experience of its capabilities, you can download the free demo version of the software.