Can I edit photos in-camera and print directly from an SD card without using a computer?

I won't recommend specific products here, but you might actually be looking for a cell phone or a tablet instead of a camera. Most cell phones do not necessarily require you to use them as a cell phone, you can also without a subscription, use them as small, portable computers.

It is relatively easy to find cell phones, or to a certain extent also tablets if you want a larger display, with quite acceptable or good cameras. For these, there are a lot of different photo editing apps, which you can install and use directly on the device. You probably won't find a device with replaceable lenses and zooming capabilities, if present at all, are usually inferior.

It will be very difficult to find a dedicated camera, on which you can install a broad selection of additional software. Many cameras have some kind of image editing functions pre-installed, but the functions are often very limited. Often, you can only manipulate brightness, contrast and colour, crop the image or apply a few effect filters. For the same price, you can however, in general, expect much better optical and image quality from a dedicated camera than from a cell phone or a tablet.

You don't write why you want to avoid transferring the images to a pc and manipulate them there before printing, but if mobility is an issue and you already have a halfways decent cell phone, you do of course also have the option to transfer the images on-the-go from any camera to your cell phone, manipulate the images and then print from there.