procedure TForm1.PrintAnExcelFileToAdobePDF(Sender: TObject);
var
   ExcelFileName, PDF_FileName: String;
   ExcelApplication, ExcelWorkbook: Variant;
begin
     //be sure ComObj and Variants units are included in the "uses" clause

     ExcelFileName := 'C:\PhysiologyWeb\delphi_code_examples\excel_file.xlsx'; //replace file name with the name of your file
     PDF_FileName := ChangeFileExt(ExcelFileName, '.pdf');                     //change pdf file name as desired

     ExcelApplication := Null;
     ExcelWorkbook := Null;

     try
        //create Excel OLE
        ExcelApplication := CreateOleObject('Excel.Application');
     except
           ExcelApplication := Null;
           //add error/exception handling code as desired
     end;

     If VarIsNull(ExcelApplication) = False then
        begin
             try
                ExcelApplication.Visible := True; //set to False if you do not want to see the activity in the background
                ExcelApplication.DisplayAlerts := False; //ensures message dialogs do not interrupt the flow of your automation process. May be helpful to set to True during testing and debugging.

                //Open Excel Workbook
                try
                   ExcelWorkbook := ExcelApplication.Workbooks.Open(ExcelFileName);
                   //reference
                   //https://docs.microsoft.com/en-us/office/vba/api/excel.workbooks.open
                except
                      ExcelWorkbook := Null;
                      //add error/exception handling code as desired
                end;

                If VarIsNull(ExcelWorkbook) = False then
                   begin
                        ExcelWorkbook.ExportAsFixedFormat(0, PDF_FileName, 0, True, False, 1, 1, False, EmptyParam);
                        //If the Excel file is blank and there is nothing to print, it will cause an error.
                        //If a file with the new name already exists, it overwrites it. Write additional code to address as desired.
                        //parameters:
                        //Type                       Required          XlFixedFormatType     Can be either xlTypePDF (0) or xlTypeXPS (1).
                        //FileName                   Optional          Variant               A string that indicates the name of the file to be saved. You can include a full path, or Excel saves the file in the current folder.
                        //Quality                    Optional          Variant               Can be set to either of the following XlFixedFormatQuality constants: xlQualityStandard (0) or xlQualityMinimum (1).
                        //IncludeDocProperties       Optional          Variant               Set to True to indicate that document properties should be included, or set to False to indicate that they are omitted.
                        //IgnorePrintAreas           Optional          Variant               If set to True, ignores any print areas set when publishing. If set to False, uses the print areas set when publishing.
                        //From                       Optional          Variant               The number of the page at which to start publishing. If this argument is omitted, publishing starts at the beginning.
                        //To                         Optional          Variant               The number of the last page to publish. If this argument is omitted, publishing ends with the last page.
                        //OpenAfterPublish           Optional          Variant               If set to True, displays the file in the viewer after it is published. If set to False, the file is published but not displayed.
                        //FixedFormatExtClassPtr     Optional          Variant               Pointer to the FixedFormatExt class.
                        //reference
                        //https://docs.microsoft.com/en-us/office/vba/api/Excel.Workbook.ExportAsFixedFormat
                   end;
             finally
                    ExcelApplication.Workbooks.Close;
                    ExcelApplication.DisplayAlerts := True;
                    ExcelApplication.Quit;

                    ExcelWorkbook := Unassigned;
                    ExcelApplication := Unassigned;
             end;
        end;
end;