Introduction
The Distance Arrow Tool is used to keep distances between frames absolutely or relatively within the document, when the document is resized.
...
The Distance Arrow can be used on the sides (not the angles) of a document by clicking on the small boxes in the center of the side. Then drag the arrow to the frame to which you want to connect the first frame.
Understanding InDesign’s default behaviour
As a reminder: With a facing page (default setting when creating a new document), the inner edge is always fixed. In the case of a horizontal change, the border on the right-hand side is shifted accordingly, and in the case of a left-hand side, the left-hand side. Vertically, the side grows or shrinks equally upwards and downwards.
...
The individual elements are moved in a different way, but they do not change their position relative to each other.
Using the Distance Arrow absolutely
If a Distance Arrow is used absolutely between two frames, it keeps the absolute distance between the frames independent from the scaling.
...
Before adaption
...
After adaption
...
Using the Distance Arrow relatively
If a Distance Arrow is used relatively, it will keep the relative distance between two frame sides relative to the degree of scaling.
...