I just downloaded a set of Glypish icons, however I'm not sure how to scale them up using Pixelmator (my only graphics editor). They give a .psd file with each image as a separate layer...
After You load the file to PXM and press V (moVe tool), then you click on a layer with an icon you want to resize and the resizing marks will appear -> press Shift and drag any point to resize the icon to any size you want.
Second way is by selecting the layer, then press EDIT->TRANSFORM (or RightClick->Transform) and choosing scaling value in the upper selection area -
