The freeware and light versions of Cadsoft Eagle limit the design area of the PCB to 10cm x 8cm. This is enough to do many projects, but when you want to try and panelize to fill a 10cm x 10 cm board, it won't work. Plus, maintaining separate projects and updating them on the panel, and maintaining consistency of labels and reference designators can be a pain.
In this Instructable, I will show you an easy way to merge Gerber files generated from Eagle (or any other EDA tool) in a way that Seeed Studio will accept them for panelizing with their Fusion PCB service. I will be using the SARduino644 v1.0 board shown below as an example.
Step 1: Design Board and Render Gerbers
When you're happy with your board, and it passes Seeed's design rules, use the Seeed CAM processor to generate the Gerbers for your PCB.
When you're done, you should end up with the following files:
<board>.GTO - top silkscreen
<board>.GTS - top soldermask
<board>.GTL - top copper
<board>.GBO - bottom silkscreen
<board>.GBS - bottom soldermask
<board>.GBL - bottom copper
<board>.TXT - Excellon drill file.
Before you proceed, you should check the Gerbers carefully to make sure everything looks right *before* combining them into a panel, this will save time later if you find a problem. I like to use the online gerber viewer provided by CircuitPeople. You can make a zip of all the files and upload them in one go, and they will all be rendered to image files.