Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

uses
   RichEdit;

 // Using the Paragraph property 
procedure RE_AlignText1(ARichEdit: TRichEdit; alignment: TAlignment);
 begin
   ARichEdit.Paragraph.Alignment := alignment;
 end;

 // Using PARAFORMAT2; nonVCL 
procedure RE_AlignText2(ARichEdit: TRichEdit; alignment: TAlignment);
 var
   pf2: PARAFORMAT2;
 begin
   FillChar(pf2, SizeOf(pf2), 0);
   pf2.cbSize := SizeOf(PARAFORMAT2);
   SendMessage(ARichEdit.Handle, EM_GETPARAFORMAT, 0, Longint(@pf2));
   pf2.dwMask := PFM_ALIGNMENT;
   case alignment of
     taLeftJustify: pf2.wAlignment := PFA_LEFT;
     taCenter: pf2.wAlignment := PFA_CENTER;
     taRightJustify: pf2.wAlignment := PFA_RIGHT;
   end;
   SendMessage(ARichEdit.Handle, EM_SETPARAFORMAT, 0, Longint(@pf2));
 end;

 // Example: Right align text 
// Beispiel: Text rechtsbundig ausrichten 
procedure TForm1.Button1Click(Sender: TObject);
 begin
   RE_AlignText2(RichEdit1, taRightJustify);
 end;