I use a Mac at home and I thought that they did have a DjVu plugin for it; I remember looking and then thinking that I couldn't be arsed.
There are other (free) ways to find out the GRO reference of your great grandfather's birth cert so you can order it (you would have to order it from the GRO (http://www.gro.gov.uk/gro/content/certificate/index.asp), you can't view the cert itself online). From checking FreeBMD (http://www.freebmd.org.uk) it looks like that entry has been transcribed: Births Sep 1862 - SEARLE Charles Samuel, Depwade vol 4b page 204. You can check the scan of the original GRO index page using the 'spectacles' link to the right of it: it looks correct, although I'm not 100% sure about the page number.
no subject
There are other (free) ways to find out the GRO reference of your great grandfather's birth cert so you can order it (you would have to order it from the GRO (http://www.gro.gov.uk/gro/content/certificate/index.asp), you can't view the cert itself online). From checking FreeBMD (http://www.freebmd.org.uk) it looks like that entry has been transcribed: Births Sep 1862 - SEARLE Charles Samuel, Depwade vol 4b page 204. You can check the scan of the original GRO index page using the 'spectacles' link to the right of it: it looks correct, although I'm not 100% sure about the page number.
Let me know if you want any more help!