Depends what Windows/OS is he running on it. If it was updated to Win10 and there are few programs running on it easy can consume 4GB of Ram.
I would say most of the time doubling memory can reduce of use virtual memory what can reduce use of SDD.
But like always to be sure if it makes sense you need to check what is going now.
The best costless way to improve a speed of your laptop is to remove apps running in background, switch off services which you don't really need like Google Updates and all similar sh..., go through the task scheduler and disable ones which are doing nothing, switch of indexing service on all your SDD/HDD.
There is a long list of tricks which can help you.
Always start with good cleaning, you wouldn't believe how often you can easily make you computer running better with simply cleaning off a bloody dust cloud collected inside for years.
It's plenty of good reading on internet if you have got time and never done it yourself before.
Other way just find a sensible local expert and he will do it for you.
I saved tens of different computers, which were OIW to a bin, just by giving a good service to them.