Several programs within the Adobe Creative Suite have a layers feature: Photoshop, Flash, Illustrator and InDesign. Their function differs from program to program but, in general, the use of layers serves to offer flexibility of composition. Items of related content can be placed on their own individual layers. Layers can then be made visible or hidden or can be locked to prevent their content being changed. Equally, the stacking order of layers can be changed to determine which elements are displayed in front of which other elements. Layers are not always necessary when creating a publication in InDesign, but they can beneficial in several situations.
Intricate page layouts often require the creation and complex manipulation of many different InDesign elements. This process can sometimes be made much easier by placing elements on a series of layers.
Perhaps the most common reason for using layers is where you need to produce several different versions of a publication. For example, there may be one version of a catalogue for in-house use and another for clients; or you may need to create different language versions of the same document.
Layers are also useful where certain page elements take a long time to redraw. For example, if you’re creating a large poster with a high resolution background image, you may find it useful to place it on a separate layer and hide the layer when you are working on other elements.
Since layers can be made none-printing simply by hiding them, it is also possible to use layers to store text and other elements which are relevant to the publication but are not to be included in the final version. Such layers could also be used for comments and reminders and can simply be deleted once the publication has been completed.
Another trick is to use layers for creating a document by using a similar publication as a template. A full sized scan of the original document can be placed on a locked background layer and used to ensure that each part of the layout is in the right place, has the right dimensions and so forth.
PowerPoint users often complain that elements placed the slide master will always be behind elements placed on the slides. Whilst the same if true of InDesign master page elements, using layers allows to overcome this fact. Simply place all those items which need to be front-most on a separate layer and move that layer to the top of the heap.