GIMP (GNU Image Manipulation Program) software is a full-featured image manipulation program, nearly equivalent to Photoshop. What sets it apart, however, is the fact that it is completely open-source and free to use. This fact makes the GIMP an excellent choice for those running on a low budget--for example, an about-to-be-married couple looking to inexpensively design invitations for their wedding. No matter what the occasion, GIMP software can ease the process of creating attractive invitations.
Install GIMP and run it. Create a new image by pressing Ctrl-N. Adjust your image's dimensions as desired--you should have about 300 pixels for every inch you want on the printed invitation.
Create a parchment-textured background. Fill the layer with a tan colour, using the bucket tool. Under the Filters menu, add noise ("Noise > HSV Noise") and blur it ("Blur > Gaussian Blur"). Add a new layer (Ctrl-Shift-N) and add fog texture ("Render > Clouds > Fog") of a darker tan than your base colour. This should give you a mottled, parchment-like look.
Give the parchment torn edges. Create another layer and use the rectangle select tool to select a large box, leaving only a small margin on each side. Invert the selection (Ctrl-I) and open "Select > Distort" to give the selection a jagged edge. Use the bucket tool to fill the selection in white, and press Ctrl-Shift-A to deselect everything. This jagged, white border will make the parchment appear to have a rough edge.
Add the invitation text, using the text tool. Type your message into the dialogue that appears after clicking on the image where you want the text to begin. Use the options in the Toolbox window to adjust the text to your desires--you may wish to give the text a centre alignment, or give it a larger, elegant font. Coloured text works well, too; just be sure it shows up well against your parchment background.
Print your invitations (Ctrl-P), using the Print Preview feature to make sure the printed invitations will be the right size, first.