Hi Joe
Layer Shifting
Create four copies on layers above the original and set them all to lighten mode
Shift one layer one pixel up
Shift one layer one pixel down
Shift one layer one pixel left
Shift one layer one pixel right
You can create as many layers as you wish and shift some by several pixels
This does not remove all the ink, but it does reduce it
I used 'dust and scratches' to remove the remainder
Once all the ink marks are gone
Select all > copy merged > paste and Add a hide all mask
Switch off all the intermediate layers and than paint onto the mask to remove the ink
One day I will write a tutorial. If I remember I will post a link here.
In the example picture that you posted I may have used 'Color DeConvolution'
It works really well on some pictures and is available here (PC only, I think)
http://home.planet.nl/~ber03728/4N6site/main.htm
(Ask Charles for a license)
Hope this helps
Ken.