Select the layout viewport that you want to modify. Right-click, and then choose Properties. If necessary, click Display Locked and choose No. In the Properties palette, select Standard Scale, and then select a new scale from the list. The scale you choose is applied to the viewport.

To Modify the Scale of a Layout Viewport Using the triangular scale grip... Select the layout viewport that you want to modify. Click the triangular scale grip near the center of the viewport, and click the desired scale from the list. The scale you choose is applied to the viewport.

In the Plot scale section, deselect Fit to paper. Select the plot scale by doing either of the following procedures. Choose one of the default scales from the Scale drop-down menu. Enter the desired values in the two text boxes, where the top one describes the paper units and the bottom one describes the model units.

In the drawing that is not at 1:1 scale, find an object or line whose length you know. Start the scaling command with SC (or SCALE). Make a selection for the objects that need to be included in the scaling operation. Click in the drawing for the first point of the scaling base (base point). Type R to activate Reference scaling.

Select the layout viewport you want to modify, then click the triangular scale grip at the middle of the viewport. Select the scale you want from the list to apply it to the viewport.