UV/Texture Editing is where you paint textures and adjust how they fit the objects (the UV mapping). It has a full image editor, with layers, effects and painting right on the model.

The texture layers are in the Layer Manager.

Tools

The tools act on the active layer.

Pointer (V): Moves and transforms the active layer.
Select (S): Marks an area. What comes next only applies inside it.
Brush (B): Paints with a soft edge.
Pencil (P): Paints with a hard edge, pixel by pixel.
Eraser (E): Erases what was painted.
Fill Bucket (G): Fills the area of similar color under the click.
Text (T): Creates an editable text layer.
Shape (U): Creates an editable geometric shape layer.

Stroke size, opacity and color are in a bar over the painting area. With text or shape, the bar shows the layer controls, such as font, fill and outline. Brush, pencil, eraser and fill do not work on text, shape or vector layers.

Menus

File

New Texture: Creates a blank texture.
Import Texture: Brings an image from your computer as a texture.
Export Texture: Downloads the texture, including PSD with separate layers and DDS and TGA for game engines.

Edit

Copy, Cut and Paste.
Select All: Selects the whole active layer.
Free Transform: Moves, scales and rotates the selection, or the whole layer when nothing is selected.
Transform Layer: Flips or rotates only the active layer.
Unwrap UV: Redoes the UV mapping of the selected object.

Image

The commands in this menu change the whole texture, with all layers.

Resize Image...: Changes the texture resolution.
Resize Canvas...: Grows or crops the texture area without stretching the content.
Transform Image: Flips or rotates the whole image.

Adjustments

Adjustments apply to the active layer, with a live preview.

Brilho..., Contraste..., Saturação... and Exposição....
Vibração...: Boosts dull colors without blowing out the strong ones.
Matiz...: Shifts the colors around the color wheel.
Níveis...: Adjusts blacks, midtones and whites.

Effects

Effects apply to the active layer.

Escala de Cinza, Inverter Cores, Desfocar..., Nitidez... and Posterizar....
Textura: Creates from the image the maps that give the material relief and shine: normal, displacement, ambient occlusion and specular.

Generate

Noise…: Generates noise, with the type and settings of your choice.
Pattern…: Generates a drawn pattern: brick, tile, cobblestone, honeycomb, checker, stripes, grid, dots, planks, herringbone, scales or diamond plate.
Paint Ambient Occlusion…: Paints the shadow of the object's corners and folds onto the texture.
Paint UV Islands: Draws the outline of the UV mapping parts, as a guide.

View

Show Vertices: Shows the vertices on the model beside it.
Show Wireframe: Shows the edges on the model beside it.
Show Pixel Grid: Shows the pixel grid when the painting area is zoomed in.