Adding graphics from other programs
InDesign supports many common graphic file formats. While this means that you can use graphics that were created using a wide range of applications, InDesign works best with other Adobe professional graphics applications, such as Photoshop, Illustrator, and Acrobat.
By default, imported graphics are linked to an InDesign document rather than embedded, which means that InDesign displays a preview of the graphic file in your layout without actually copying the entire graphic file into the InDesign document.
There are four major advantages to linking graphic files. First, it reduces the size of InDesign documents because they don’t need to include the data for embedded images. Second, you can edit a linked graphic in the application you used to create it, and then simply update the link in the InDesign Links panel. Third, it enables everyone using a graphic to be alerted when that graphic has changed. Fourth, it saves disk space. Updating a linked file that has been modified maintains the current location and settings for the graphic file and replaces the preview image in InDesign with the updated graphic’s preview.
All linked graphics and text files are listed in the Links panel (Window > Links), which provides buttons and commands for managing links. When you print an InDesign document or export a document as an Adobe Portable Document Format (PDF) file, InDesign uses the links to produce the highest level of quality available from the original, externally stored versions of the placed graphics.