Just for interest - this is the number of PDF guides downloaded from the Peak District Caving web site during November. Some are bound to be idle downloads but the numbers mirror the popularity of the caves quite well. So PDF seems to work for some......
131 Giant's Hole Part 1 (The Entrance to Garlands Pot)
75 Stoney Middleton Cave Index (main index of locations and access info)
75 Castleton Cave Index (main index of locations and access info)
63 Oxlow Cavern
55 Giant's Hole Part 2 (Garlands Pot to Eating House and The Upper Series)
49 Titan
48 P8
42 Peak Cavern Part 1 (The Main Stream Cave and Far Sump)
41 Lathkill Dale Cave Index (main index of locations and access info)
35 Sidetrack Cave
34 J.H. (James Hall's Over Engine Mine)
32 Eldon Hole
31 Caves of Cave Dale
31 Rowter Hole
31 Gautries Hole
30 Odin Mine
30 Bradwell Area Cave Index (main index of locations and access info)
24 Speedwell Cavern Part 1 (The entrance to Main Rising & Cliff Cavern)
21 P7
21 Hangover Hole
20 Peak Cavern Part 2 (Victoria Aven)
16 Peak Cavern Part 4 (Pickering's Passage)
16 Peak Cavern Part 7 (Treasury and the links to Speedwell Cavern)
16 Speedwell Cavern Part 3 (The Assault Course & Pilkingtons Series)
15 Peak Cavern Part 8 (The White River Series)
15 Speedwell Cavern Part 4 (The Bung Hole Series)
15 Speedwell Cavern Part 2 (The Halfway House Series)
15 Speedwell Cavern Part 5 (Wirlpool Passage)
15 Peak Cavern Part Part 5 (The Galena Chamber Circuit & the NCC Shafts)
13 Peak Cavern Part Part 6 (Lake Passage and Ink Sump)
12 Peak Cavern Part Part 3 (Far Sump Extension)
http://www.peakdistrictcaving.info/peak_district_cave_information.htm