from the first beginning by using only five different notes and treble clef, to more advanced studies that claim abilities from better note reading to small position changes and left right coordination.

While this collection is on growing, it is only providing the single pieces as lilypond *.ly files.
PDF and MIDI files are going to be added within the finalization of the collection to prevent a boost of the .git repository.
If you want to get PDF files beforehand you need to install lilypond and compile the *.ly files.

Here is a short description for a LINUX System from the Command-Line

# install lilypond from your repository
# using apt or your apropriate package manager

apt update
apt install lilypond

# compile input file with lilypond

lilypond filename.ly 

# to batch compile all files in a folder
# simply run this for-loop from the command-line

for i in *.ly; do lilypond $i;done

If you want to get MIDI files, you need to compile the files within the single-page folder. You could batch compile those as described above or just compile the files you need. Please note, that the peices up to Nr. 16 are very short educational pieces and you will get a lot of white space on the PDFs.

typset with: Lilypond "2.18.2"

you can try it online on: LilyBin or get support at the offical IRC on FreeNode
more Scores in the LilyPond format can be found on www.MutopiaProject.org
snippets and tweaks can be found in the The LilyPond Snippet Repository ♪♫