First, read the English article below.

If you have the paid version of Adobe Acrobat installed, you can use it to split your PDFs. You can't split PDFs with the free Adobe Reader, so if that's all you have you'll need to use one of the other methods in this article. This will open the Tools panel.   Acrobat allows you to split by a pre-determined number of pages. For example, setting the split at 3 max pages will split the document into separate files of 3 pages each. You can also select to split by your bookmarks, or by a maximum file size. Output Options button to select where you want the new files to be saved. You can save to the same folder as the original file, or you can select a new folder. You can also set how you want the new files to be labeled. OK to split the file. Your new files will be placed in the location that you set in the previous step. 

Now, please write a short abstract for it in Vietnamese. Abstract:
Mở tài liệu PDF mà bạn muốn tách trong Adobe Acrobat. Nhấn vào nút "Tools" (Công cụ) ở phía bên trái của cửa sổ. Mở rộng phần "Pages" của bảng này. Nhấp vào nút "Split Document" (Tách tài liệu). Đặt số trang mong muốn của từng tệp mới. Nhấp vào nút . Nhấn .