I have investigated and is not a problem of the charset of database. If I write the arabic characters directly in DB, when I load the page, appears correctly. The problem is that Liferay save the arabic values like ?????. With chinese characters happens the same.

I had a similar problem. I figured out that collation of columns name and title of table Layout is SQL_Latin1_General_CP1_CI_AS. They need to be SQL_Latin1_General_CP1256_CI_AS to show Arabic (and also Persian) page names correctly. So I used the following queries to modify their collation:

ALTER TABLE Layout ALTER COLUMN title varchar(2000) COLLATE SQL_Latin1_General_CP1256_CI_AS
ALTER TABLE Layout ALTER COLUMN name varchar(2000) COLLATE SQL_Latin1_General_CP1256_CI_AS

Then I modified the name of the page and the problem was resolved. Never ever modify the database manually. It causes Liferay indexes get invalidated and it can make problems.