Windows 8 reserves a % or 2gb whichever is smaller for the paging file by default, this is more than enough for most use-cases.
@Bob Eyster - you should read http://blogs.technet.com/b/markrussinovich/archive/2008/11/17/3155406.aspx
The issue has absolutely nothing to do with the paging file. It's 2/3rds empty when getting this error. What appears to be happening is that the initial 4gb, which is available for 32bit applications, is being used by the 64bit applications causing it to think it's going to run out of 32bit addressing space once it hits the 4gb limit. In reality the 64bit applications should be pushed into the 2nd 4gb space to make room fro the 32bit applications. Unfortunately this error message doesn't seem to recognize the difference between the two and reports the error erroneously. Calculating just the 32bit apps they are using less than 2.3gb of addressing space with 64bit using the remaining 0.9gb.