@Galenbo
The scan image approach is by no means easy as the PCB has to be stripped bare of all components first, and if it is a multi-layer board, it must be sacrificed i.e. peel off layer-by-layer carefully, a task that requires skill and steady hands, especially if the board is very dense and contains many hidden or buried vias, which is quite a challenge in itself. Tell me if any customer is prepared to let you do that to their last piece of spare PCB!
From what I gather from the company, they only produce the gerber files in order to facilitate re-production of the bare board. To re-construct the schematic diagram involves another tedious task of identifying and assigning the various component footprints to the gerber data in a CAD-CAM software like CAMtastic, then converting and importing it to the PCB layout design file format of a target CAE tool such as Altium Designer, cross-referencing the parts to Altium's schematic library symbols (ICs with multi-parts can be tricky), before you can back-annotate to create the draft schematic of the PCB.
It may sound simple but actually quite a number of processes are involved after importing the gerber and NC drill data, such as layer type assignments, board stack-up and drill sets, netlist extraction (the success of this step depends on the accuracy of the preceding steps mentioned), handling split plane sections (if nested planes are present, your CAE software may not even support it!), etc. Even when the draft schematic is generated, you still need to do a physical electrical connectivity check with another good PCB to verify the accuracy.
So besides the learning curve involved in using the CAE software, you need to have a good understanding of PCB structural designs to carry out the steps outlined above. There is no quick fix like an automated one-click solution that converts gerber data straight to schematic solution. Even for a simple double-sided PCB, I find that doing the manual way is still the fail-safe and most effective approach.
Singapura