To use your scanner under Arch Linux install SANE (Scanner Access Now Easy):
sudo pacman -Syu xsane-gimp
With xsane-gimp you also get a simple frontend (xsane) and a Gimp plugin.
Another useful frontend is simple-scan:
sudo pacman -Syu simple-scan
For HP scanners there is a metapackage which already contains most of what you will need to scan (in fact, HP website considers this as de facto Linux drivers for its devices):
sudo pacman -Syu hplip
Check whether your scanner is supported: http://www.sane-project.org/sane-mfgs.html
You can run one of the frontends with xsane or simple-scan, or use a command line interface.
Check whether sane recognizes your scanner: scanimage -L
Scan image: scanimage --format=png --output-file test.png --progress
Scan image with a specified device: scanimage --device "pixma:04A91749_247936" --format=tiff --output-file test.tiff --progress