If Hillary is charged while Obama is in office, he can pardon her of any such crimes. That’s what Ford did for Nixon – click to read.
But once Obama is out, and even if Hillary is in the White House, then she’s stuck.
And while Obama could issue a pardon now, doing so would be tantamount to saying she is guilty. That would undoubtedly affect the election.
Any criminal charges against Hillary must, therefore, wait until after Obama leaves office.