Only if you know for certain that you are running out of memory in specific circumstances. Open Windows resource monitor and click on the memory tab. Open all your normal stuff like you would always do and see if you run low on memory. If you don't, then adding memory probably isn't going to help much. I honestly think though that having 8GB of memory should really be a bare minimum these days.
At 4GB, depending on which operating system version and which bit version of it you are running, 32 or 64 bit, it's probably a bit low for todays machines. If you have a 32bit version of Windows, 4GB is all you can use anyhow.
My best advice for improving laptop performance is to replace the HDD with a ssd.
Samsung makes this easy to do.
Extra ram is always helpful and 4gb is not that costly.
A ram site such as Kingston will advise you what updates are compatible with your laptop.
A second stick will allow you to operate in dual channel mode which is good for the processor, and is particularly good for integrated graphics.
I will wholeheartedly second the idea that adding an SSD in place of the existing hard drive, if you don't already HAVE an SSD, is probably even more important that adding more memory, UNLESS you are running applications or doing heavy multitasking and you KNOW you are running out of memory.
In that case, obviously the faster storage isn't going to stop the lack of memory resources, so then memory is the obviously bigger factor. Otherwise, I'd do an SSD first, memory after that.