Yes, you can select everything in your drawing using several methods.

Set a Custom Gesture

1. Go to Settings > Gestures.
2. Assign 'Select All' to a two, three, or four finger tap.
3. Return to the canvas and perform the gesture to select everything.

Use the Lasso Tool

1. Zoom out on your canvas until the entire drawing is visible. The maximum zoom out is 5%.
2. Select the Lasso tool.
3. Ensure All Layers is active in the Selection menu at the bottom of the screen.
4. Draw a loop around all of your content to select it.

Select by Layer

1. Open the Layers menu.
2. Tap the active layer to open its options menu, then tap the selection arrow icon to select everything on that layer.
3. To add another layer's content, tap a different layer in the menu once to make it active.
4. Tap it a second time to open its options, and tap the selection arrow to add its contents to your current selection.
5. Repeat for all layers you wish to select.