on separate partitions on the same hard drive, you cannot run both at the same time.
That said, it is possible to access the documents created by Pages and Numbers that are housed on the "other' partition.
The applications themselves must be installed separately on each partition.
eg. Partition A has 10.6 and you install iWork, create documents and presentations and save them in your Documents folder on Partition A
Partition B has 10.7 installed. iWork needs to be installed on this partition too. Create documents and presentations and save them in your Documents folder on Partition B.
Now, depending on which partition you are booted from, you can launch Pages (for example) and tell it to open a document that is in your documents folder on the other Partition. Edit and save it back to the same place.
Long story short, all the apps you want to be able to use on either partition, must be installed on each of those partitions.
Question. Why didn't you just update from 10.6 to 10.7 without the hassle of creating a separate partition?
I have a Macbook running Snow Leopard. I created a partition and loaded Lion 10.7. That is all I did. Is there something else I need to do in order to access my apps? Pages won't open, Numbers.. etc.. Because of this, I am continuing to use Snow.
Is it possible to use the same app from either system?