My impression was that the lack of an organization system beyond a "personal documents" folder makes him feel like he can't carry more than a few. I have a lot on mine as well. . .though perhaps not as many as you, Andrys!

. . .
Mine is almost empty compared to what a few of the denizens of these boards have on theirs! :-)
I've found the key is making sure the PDF has a very useful name so I can find it when I want. The PDF retains that name when you put it on the Kindle. So, for example, one of my doc's is called "Care and Feeding". . .well, it has to do with guitar care. I'll most likely re-name it to something a little more descriptive -- at least putting the word 'guitar' in the title -- so that it's more obvious on the list what it is.
As a corollary, one could use a rudimentary 'tagging' system by making the first word of each title an appropriate category. So the guitar documents would be called "guitar -- care and feeding" and "guitar - Open My Eyes", etc. and the keyboard arrangements could say 'keyboard' as the first word and so on. I also have some that are metro maps and users guides. By using clever naming, the similar documents will all come up near each other when sorted by title.
All my sheet music pdf's are prefaced by 'sm' so I can see them all together... great minds...!
That makes for less typing but you do have to remember what the prefix means :-)
but kb is probably memorable.
Which reminds me, I finally took some images of some DX screens
including two for sheet music, portrait and landscape.
That blog entry is at the top of the blog as of yesterday.
I didn't do good pics of the DX doing generic text when showing it with a K2 or K1 because I forgot I had put it into Font #2 mode, which is small and crowded! I'll have to add some more.
Will probably add later a couple I took with the Mighty Bright on it too last night.