Resize Magic full review
If you can’t afford the more commercial options here, check out this affordable plug-in. Resize Magic has plug-in and script versions with the same interface, although the interface is extremely basic and the functionality limited.
The options on offer are to increase the size based on the pixel resolution and to specify the smoothing. There are no document presets or even guides as to how large a 300dpi image would be. The new resolution is automatically constrained so you don’t have to type in the other half, but that’s all it’s got.
Resize Magic is cheap but that shows in its lack of functions and control