Photoscape is in my opinion the best free and most professional photo-editing application, which I know.
If I want to select and to move a text object and change the font size in pictures I have best experience with PhotoScape. Beside many other very useful features you can perfectly select, move and manipulate text objects. This and the framing of text fields is a problem for many other free photo-editing software products as Paint.net, Pixlr, Adobe Photoshop Express, GimpShop or IrfanView. My recommendation for this purpose (e.g. commenting of screenshots) and especially for the professional framing and renaming of large series of photos is Photoscape.