Is it possible to increase the resolution of an image without expensive software?

"Yes.

Something like this: SmillaEnlarger

Will do it without just making a blurry mess too. There are other fractal enlargers out there which try to mimic missing detail - but this one is free."

There's a nice online one here http://waifu2x.udp.jp/ which uses "Deep Convolutional Neural Networks". It's especially good for enlarging logos and line art.

"Sorry everyone - but you CAN NOT increase resolution on something.
Why do people think you can? If the information is not there in the image - how is photoshop or something going to find it and add it in???? IT CAN'T.
It's a give and take relationship that resolution and physical size have.
You got something at 8.5x11 (physical) and 300dpi - you blow it up to 14x16 - guess what, it's going to be way less than 300dpi not matter what you try to increase. Vice versa it will work great. Basically You can take away but you can't add to. That's the real truth. Do your tests and prove it to yourself.

Don't answer questions you don't understand. All these ""experts"" out there. Just cause you own a toothbrush, doesn't make you a dentist.

Again - something that is 72dpi at 7inches will most likely be around 37dpi at 14inches. Give and take. Start your original as high as you can (be it a scan or photo) and keep it b/c that's as large and as good looking as it will ever be."

"YES YOU CAN! I used GIMP and its free.

Open up a NEW project and set the dimensions you need, then use a pixel size of like 300x300 (no less)
Open up the image you want as a LAYER and match the size of the original canvas (above).

DONE!!!

I guess I should get my dentists license now."