Does the MDI have any other child ? If not, you can use
to place the two childs side by side. If you need to specify the size, use the child forms' width, height, left and top properties before arranging them.

Hi thanks for the help, now I would like to display a pdf file, do you know how?

To open a pdf file, or any other file which has a program associated with it, from VB, use the ShellExecute API Function.

If you want to display the pdf within your form, you either have to use an ActiveX control that can do it for you, or write the code to decipher and display the pdf file urself

Hi thanks for the help.the ShellExecute is work fine.
but the window is floating outside the mdi,

since I use
lRet = ShellExecute(Me.hwnd, vbNullString, "c:\AN-H02.pdf", vbNullString, "c:\", 1)
can I pointing Me.hwnd to a mid child form? and how?

As far as I know, you cannot use a child window hwnd for opening a separate program. ShellExecute will launch the associated program with the file specified (Adobe Acrobat usually for pdf files). You cannot open a separate application in a child form