I want to display pdf file in Citect SCADA

You could display a web browser on a page in your project. Just set the web browser URL to the path/filename of the PDF file and it will use whatever PDF viewer it has to display it. The exact method depends on the version of Citect/PlantSCADA you're using.

Another option is to open the PDF viewer as a separate app. See the ExecEx() Cicode function in knowledge base article TN28950. You'll have to search for it. The link keeps getting deleted from my message.

You just tell it the path/filename and Windows will open the registered PDF viewer.

Here's the Cicode function since this forum is blocking the link:

INT mhShellExecute = -1;

// Run an application or opens a file, folder, shortcut, email, or web page with the associated application
//
// Arguments:
//
// sFile           Name of the file, folder, or web page. May contain path substitutions
// sParameters     List of parameters if running an application (default = "")
// sOperation      Action verb for file associations. Right-click on the file in
//                 Windows Explorer to see the available options. For example:
//                 "edit"     Launch the editor for the document
//                 "explore"  Open Windows Explorer for the specified folder
//                 "find"     Open Windows Find dialog
//                 "open"     Open the file, folder, or application (default)
//                 "print"    Print the document
// sDefaultFolder  Default folder for the application to use. May contain path substitutions
// iMode           Request that the application window opens in a specific state:
//                 0  Hidden
//                 1  Normal (default)
//                 2  Minimized
//                 3  Maximized
//                 4  Recent size & position
//                 5  Current size & position
//                 7  Minimized (active window remains active)
//                 10 Default state
//
// Return Value:
//
// 0   No error
// 2   File not found
// 3   Path not found
// 5   Access denied
// 8   Out of memory
// 11  Corrupt exe file
// 26  Sharing violation
// 27  File association invalid
// 28  DDE timeout
// 29  DDE failed
// 30  DDE busy
// 31  No application associated with the file or operation
// 32  DLL not found
//
// Examples:
//
// Open Windows' Find dialog:             ExecEx("", "", "find");
// Open Windows Explorer for c:\windows:  ExecEx("c:\windows");
// Open a document:                       ExecEx("[data]:report.xls");
// Print a document:                      ExecEx("c:\doc\report.doc", "", "print");
// Open an application:                   ExecEx("notepad.exe");
// Open a web page:                       ExecEx("">http://www.citect.com");
// Create an email message:               ExecEx("mailto:test@microsoft.com");
// Open a shortcut:                       ExecEx("c:\documents and settings\all users\start menu\My Application.lnk");
// Run a DOS command:                     ExecEx("cmd.exe", "/c ");
//
INT
FUNCTION
ExecEx(STRING sFile, STRING sParameters = "", STRING sOperation = "", STRING sDefaultFolder = "", INT iMode = 1)
    INT hWindow = WinGetWndHnd();
    INT iError;
    IF mhShellExecute = -1 THEN
        mhShellExecute = DLLOpen("shell32.dll", "ShellExecuteA", "JJCCCCJ");
    END
    sFile = PathToStr(sFile);
    sDefaultFolder = PathToStr(sDefaultFolder);
    iError = DLLCallEx(mhShellExecute, hWindow, sOperation, sFile, sParameters, sDefaultFolder, iMode);
    IF iError > 32 THEN     // Any value over 32 means success
        iError = 0;
    END
    RETURN iError;
END

If you are using v8.40 or later, you can use the built-in Web Content control. 

• Insert Web Content on a page from Tools Panel or Object from Top Menu in Graphics Builder
• Add a button to the page
• In the button action, DspWebContentSetURL(AN of the web content control, "c:\temp\MyFile.pdf");

DspWebContentSetURL(INT nAN, STRING sURL)

nAN:

The AN where the Web Content control is displayed.

sURL:

A valid URL (maximum 255 characters).

You can manipulate sURL with your code to select different pdf files.

If you are using v8.40 or later, you can use the built-in Web Content control. 

• Insert Web Content on a page from Tools Panel or Object from Top Menu in Graphics Builder
• Add a button to the page
• In the button action, DspWebContentSetURL(AN of the web content control, "c:\temp\MyFile.pdf");

DspWebContentSetURL(INT nAN, STRING sURL)

nAN:

The AN where the Web Content control is displayed.

sURL:

A valid URL (maximum 255 characters).

You can manipulate sURL with your code to select different pdf files.