I just want to note that the "document" folders functionality is rather primitive. Apparently it has been this way for a long time.
I was pleasantly surprised to see that something like this is included. This is my first time installing PortableApps.
However, as Windows systems these days have at least 4 default "libraries", namely: "Documents", "Music", "Pictures" and "Videos", I would argue that having only three (with "Documents" acting as the root of those other three) is rather disingenious (I mean the antonym of "ingenious" ;-)).
For me, and I believe many others, "Documents" or "My Documents" is a place for text material, differentiating itself from the other types. So we could have at least four "proper" subfolders.
That said, there is a host of ideas one could have on improving this functionality. I won't go into all of that now, but a wildly interesting idea I am thinking of now is to have some companion software to PA that would create an overlay filesystem to NTFS that would allow files (from e.g. the regular library locations on a Windows system) to be moved into e.g. a TrueCrypt container on the PA device. If you are only using PA portable apps then no reference on the host system should remain if the files are also securely deleted from the host system. Taking into account any journalling NTFS might do and all that. This would make it easy to work on your host system for a while all the while using your portable apps. Then when you need to secure your system again you would mount the overlay FS from the TrueCrypt container - this would also display all existing files in that regular Windows document hierarchy. You'd have an extension to Windows Explorer that would display a little icon on each file indicating whether it belonged to the overlay FS or the regular FS. Then it would be easy to securely move new files into the overlay FS with a simple right-click context menu operation. The overlay FS itself would be stored in a volume file. This could be any regular image file format like ISO or something more useful such as perhaps even a TrueCrypt container. But typically a TC container would require mounting as a drive letter (in Windows) and while not problematic (it would allow browsing of the disjunct overlay FS in isolation) you would probably not want that to be a necessity. You'd want to mount a volume file directly as that overlay FS. Typically that would involve the volume file storing a directory structure relative to for example the root of the FS you are overlaying. In an advanced incarnation this overlay software could perhaps even be able to prioritize itself over the regular FS when new files are created in designated locations.
It could then safely, securely, and reasonably portably, create a virtual "library" folder structure pretty much replacing that of the host system. Upon mount, it would replace the pre-existing folder structure of the host system, mask it, and offer its own version instead. Then you would basically have a TrueCrypt extension system that is capable of mounting "shadow" locations into the regular visible filesystem that will simply disappear again (and reveal the existing host structure) once it is dismounted.
You can then have truly secure, portable (or hidden) devices that integrate seamlessly with any host system (you may need to configure locations) and that will simply 'vanish' from the host system when dismounted and disconnected or hidden.
Without requiring the installation of hidden operating systems, that is.
Once you dismount that/those overlay FSs and subsequently dismount the TrueCrypt volume you have hidden in your encrypted device/partition, all the while leaving (perhaps) your encrypted host device mounted, there should be no traces of anything you have been doing. You would be able to allow people to mount your encrypted host device without much issue from your side, but they would not find anything useful.
Of course, this is more a feature of encryption technologies, but coupled with PortableApps it makes proper "traceless" computing possible....
It is just an idea I came up with after seeing what PortableApps could do (or actually, a little before I installed it).
But in any case: this primitive "documents" functionality in PA would at least become a bit more usable and congruent with how people want it to be done, if there are FOUR subfolders instead of THREE. The main "Documents" folder could then simply be renamed "Libraries".
I mean it is just a simple idea, but as the functionality is already there (you just cannot configure it) and from what I've read scarcely any "portable app" actually knows about the "Documents" folder (most have their own "Data" folder) it should not be all that hard to improve at least this little thing. Then it would act more like a proper mirror of the Windows "Libraries" functionality. (Which seems to be the intent anyway). (And it is congruent with how Mac OS does it as well).