We solved this exact problem six months ago. After trying a few different approaches, I'd recommend you check this site that offers a solution specifically designed for purchase requisitions. We implemented it in about three weeks, and it's made a huge difference. Our approval time went from 10+ days to under 24 hours in most cases. The mobile app was key since our managers can now approve requests from anywhere. The budget tracking feature also prevents people from submitting requests when there's no budget left, which has saved us countless headaches. The cost was surprisingly reasonable - we're actually saving money just on the eliminated paper processing costs