Please remember since you're working with Gerber there is no intelligence (just basically pads, and traces) so you're just going to be editing raw data. Please view my tutorial below as I demonstrate the following on component refdes "J25":
1. Enlarge the Drill for a single part. Place FAB 3000 in NC Editor mode since we're working on Drill data. Determine the diameter for the new drill, and assign the editing Drills I wish to reference the new Drill Tool Number.
2. Enlarge the Pitch.
Note: For best results turn on the Grid (Menu: View / Grid...) and set a value that is usable for your new pitch. I chose 10 mil as a default. I also turned off the Drill drawing layer "ALLMUSE*.drl" as this is unnecessary data for editing. FAB 3000 includes "grip" points so you can drag traces at their vertices and anything that intersects at that vertex will move also.
3. Re-rout traces. FAB 3000 includes "grip" points so you can drag traces at their vertices.
Note: Since this design is somewhat simple I'd recommend just deleting the traces and re-draw from scratch.
Note: Some users who are more CAD familiar will export the design as a DXF from FAB 3000 - open a CAD tool like AutoCAD or Draftsight; perform edits in a familiar environment and then import the DXF back into FAB 3000.
Thanks again, and please let me know your results.