Re: document permissions after changing server
I have not used Cpanel for quite a while so I used https://cpanel.net/demo/ to check. You can set the permissions using the File Manager, 755 is probably the correct permission setting for the folder. 644 should be OK for the files in the folder. The Owner and Group maybe should both be "apache"? Check what the other file's owner and group are.
You could use phpmyadmin to cross check the real file names with the Tiki assigned file names. Table tiki_files has one row for each file. There more columns than I will list, but these are the ones you can check to make sure the file is in the directory. Also, I will uses the first file on the page link you originally gave for an example of what should be in the fields. The first file on that page, "Rapport activité Plein Milieu 2009-2010.pdf" has a fileId of 121.
Columns:
fileId - value: 121
filename - value: Rapport activité Plein Milieu 2009-2010.pdf
path - This is the Tiki assigned name of the file in the directory.
Take the value of the "path" column and verify that a file of that name is in the directory you are working with.
Tom