I want to increase the size of the small drawings i do from my epson 1250 scanner to my canon 1800ip to a4 printout size is this possible.

You have to scan the pictures with a higher resolution to be able to print them in a larger format with acceptable quality.

If your default scanning setting is, say, 150dpi resolution, and you want the picture to be enlarged twofold, then you have to increase the resolution to 300dpi. If you have 300dpi now, increase it to 600dpi.
Some scanner utilities do a fully automatic scan - then you have to find the automatic scan settings and change the default resolution. Or better yet, find an option for a non-automatic scan, where you are presented with various options after the preview scan has been done. There you can usually set the desired size, resolution, improve contrast, sharpness etc.

Generally, the higher the scanning resolution, the more detail you have on the picture, and the higher magnification you can obtain when printing without quality loss.

But there's a catch - a picture in higher resolution produces a bigger file on disk - the file size grows faster then the resolution - a two times bigger picture will be four times bigger on disk. So you have to make sensible choice.