Have you bothered to wipe it clean and restore all your apps & data completely? The iPad is a computer too...and after time, things just need to be cleaned up.
Moderator Edit: your first paragraph, considered argumentative as well as disrespectful to a Moderator, has been removed. Please read the Personal message sent to you.
Enough with the speech? Good, so let's talk facts. Too many people use the word "memory" without really knowing what it means. This user was asking about RAM, not storage. If you think about a desktop computer, storage is the space on your hard drive, or these days, SSD. In the case of the iPad it is an SSD. What does that mean? Without getting two technical, an SSD is a lot faster than a hard drive because it has no moving parts. When you are talking 16, 32, or 64 GB on the iPad, you are talking about the SSD. This is for long term storage, and does not play a part in a system crashing it is close to full, because there is no room for swap. Before I explain swap, I'll have to explain RAM.
RAM is volatile, which means that when you turn your iPad off, everything in it gets wiped. RAM is what talks directly to the CPU, and is much faster that an SSD or a hard drive, but it is also very limited on the iPad because it is so fast. Basically, RAM requires a constant electrical charge to operate, and the more RAM, the more electricity required. Electricity does one thing very well, and that is to create heat. Until more efficient RAM is invented which dispenses less heat, portable devices which have no fans will have limited RAM. The iPad 3 that I use has 1GB.
So what is Swap? Swap is an area on your SSD which is used to swap what is in RAM into temporarily, so that an app requesting something on the SSD can get into RAM. This is called paging, and this is what slows down a device more than anything else. If you run out of RAM and don't have enough swap, things start to crawl or crash.
Now, to answer your question, I only wish you could add more RAM to an iPad. But right now, even of you could, you would have paid a lot more for it and it would be running a lot hotter. Your battery life would also plummet, and the amount of heat generated would harm the internal circuitry. So why is your system slow and crashing?
1) How many apps do you have open at the same time? Not how many you have installed. How many are open?
2) Is your storage space full or almost full?
3) have you tried clearing your browser cache? Sometimes bad stuff gets in there, and what is supposed to make your iPad faster when browsing is actually loading services into RAM that are destructive, and CPU intensive.
4) How is your bandwidth? Have you tested your network connection lately, or is this strictly a standalone problem?
5) It could be poor programming. Free apps are great, but they are prone to memory leaks due to fewer quality controls. Memory leaks occur when a program encounters a situation that wasn't thought of by the programmer, and it starts eating available RAM, or not releasing RAM when it closes or, it's child processes close.
As mentioned above, cleaning off your iPad might help with some of these, but I wouldn't get that drastic yet. Instead, try to isolate what is causing grief, and attack that directly instead. Otherwise, you may temporarily fix your problem and wind up not reporting the errant app to the developer, and just wind up frustrated again.