Simple question, quick answer: Vectors.
:Grin:
InkScape is a vector program, similar to CorelDRAW, but it is completely free. This enables you to produce vector graphics (line drawings) or recolour vector images or PDFs with line drawing rather efficiently because you won't have to convert the drawings into bitmaps. This maintains the quality and sharpness of the original and keeps the file size small. My Viper Mk. I for example is a vector drawing (but I made it with Corel).
:Grin:
InkScape is a vector program, similar to CorelDRAW, but it is completely free. This enables you to produce vector graphics (line drawings) or recolour vector images or PDFs with line drawing rather efficiently because you won't have to convert the drawings into bitmaps. This maintains the quality and sharpness of the original and keeps the file size small. My Viper Mk. I for example is a vector drawing (but I made it with Corel).