I think the amount of memory consumed will depend on the number of products deployed, and in the case of PDF Generator, I would imagine the number of native conversion applications. My server with Acrobat and full Office conversion support usually uses about 800-900MB idle.
How many products from LC7 did you have installed when you reached the figure of 131,000K? I've just restarted a PDFG/ARES LC7 machine, after a reboot it uses 350MB for just two products.