Adobe Acrobat 7 Professional - Manual (Page 493)

Merging layers
You can merge one or more layers in an Adobe PDF document. Merged layers acquire the
properties of the layer into which they are merged (the target layer). The merging of layers
cannot be undone.
To merge layers in a PDF document:
1. Click the Layers tab, and select Merge Layers from the Options menu.
2. In the left pane (Layers To Be Merged), select one or more layers to be merged. Ctrl-click
(Windows) or Command-click (Mac OS) to select multiple layers, and click Add. Click
Add All to merge all layers.
3. To remove a layer from the center panel, select the layer or layers. Ctrl-click (Windows)
or Command-click (Mac OS) to select multiple layers. When your selection is complete,
click Remove.
4. In the right pane (Layer To Be Merged Into), select the layer into which to merge the
selected layers, and click OK.