Under the "Preferred languages" section, click the + (Add a language) button.

It was a quiet Tuesday evening when Sami, a translator based in Cairo, decided it was finally time to fix his Windows 10 Pro 64-bit machine. He had been putting it off for weeks—the constant pop-ups in English, the right-to-left text that displayed backward in preview panes, and the keyboard layout that forced him to hunt for Arabic letters in a virtual on-screen grid.

: Check this if you want the entire Windows interface (menus, dialogs) to appear in Arabic.

To summarize the search intent of "download arabic language pack for windows 10 pro 64 bit upd" :

There are two main methods to download and install the Arabic language pack for Windows 10 Pro 64-bit: