Why should I replace the folder when they are the same?...The showkase version I downloaded from the received link already is a Pro Version, isn't it? If not, where could I found the 'Pro jbcore folder' so I can replace the folder pointed in the path above?
You have purchased and are using Showkase-Standard (not Showkase-Pro).
You can check by looking at the text below the login panel on your Showkase admin login page. (Showkase-Standard displays only 'Showkase 1.2.0' whereas Showkase-Pro displays 'Showkase-Pro 1.2.0'.
Showkase-Standard comes bundled with Juicebox-Lite and SimpleViewer-Standard (the free versions of the image viewers) and Showkase-Pro comes bundled with Juicebox-Pro and SimpleViewer-Pro. (The only difference between Showkase-Standard and Showkase-Pro is the bundled viewers.)
But, in the step #3 says:
"To upgrade Juicebox upload the Pro jbcore folder, replacing:
admin/plugins/juicebox/master/jbcore"Could you please explain it better?
You need to swap the entire Lite 'jbcore' folder in your 'showkase/admin/plugins/juicebox/master/' directory with the Pro 'jbcore' folder from the Juicebox-Pro download zip package ('juicebox_pro_1.3.3/web/jbcore/').