Is it possible to extract pcb layout from an already made PCB?
I've not heard of any software that can outright convert image(s) to a netlist nor gerber files. Such a software may be theoretically possible, but it would be exceedingly difficult to write, so simply hasn't been.

What I would do... and this requires some affinity for photo-editing:


Take high-quality photos of both sides of the PCB. Preferably using a tall copy stand.
Make sure both sides are precisely aligned to reduce visual distortion.
Load the images into a photo-editing suite such as Adobe Photoshop or GiMP.
Make the images separate layers, say Layer2 and Layer4.
Flip the back side image (layer 4) horizontally.
Stack the images precisely on top of each other.
Create two additional layers, 1 and 3, onto which you can draw.
Increase the transparency of all layers.


At this point you can easily see where everything connects, as it is now truly see-through. 


If the goal is schematic capture, just quickly sketch overtop each layer's traces (onto layers 1 &amp; 3, use separate colors for each), add component pin numbers and outlines, part numbers, values, etc. Then hide layers 2 and 4, print the resulting sketch, and use this as a guide to enter the schematic. Use a pencil to scratch off each trace as it is entered into the new schematic. 


I'd prefer this method, as once the schematic is entered, a great deal of PCB design and checking work is done for you by the CAE software, and the output is guaranteed to match the chosen footprints. Today with the advent of services like OSHPark, I'd not even waste time trying to fabricate the PCB myself. (Just send them the gerbers, they do the rest.)


If the goal is just PCB duplication, then many CAE softwares will accept importing images. KiCad for instance includes a "Bitmap2Component" tool, intended for logos. Using the prior steps, exactly trace where you want copper to exist for each side onto 1 &amp; 3. Un-flip the back side image. Convert to black-and-white, then save as bitmap files. Import these in your CAE software as "components" and place one of each in the schematic editor. Save, then look at the PCB design. Place the "back side component" onto the back of the PCB. With a lot of patience and some luck, this might work. In KiCad, you may need to tweak things to make the "component" appear as a copper layer and not a silk. If drill holes are needed, it would probably be easiest to define these as separate parts and place them as needed.


I'd not recommend this route because of manual hole alignments, and indeed the whole board will be highly dependent on the camera. Parallax and barrel distortion manifest in all cameras; the only way to mitigate these is with a very long focal-length zoom lens or specialty camera.

Finally, once this project is complete, I'd take all the files generated and feed them into PaperBack and laser-print hard copies. File this away in the attic. Then in 20 more years when you need the files again, get the paper from the attic, scan them in, and convert back to files. Magic!