Hello Djalil!
The best tool for what you're wanting to do is likely the Scale button. While you won't be able to put in a percentage, you could enter a scale factor. For example, if you want to double the size of a feature, you'd enter a scale factor of 2. The Scale button is not available by default on any toolbar, but you can add it in using the customize menu using the instructions below.
Adding the Scale button to ArcMap:
1. Click the Customize menu at the top of ArcMap and choose Customize Mode.
2. Switch to the Commands tab on the new Customize pop-up window. You will need to let this load for a moment.
3. Search for "Scale" (without quotes) in the top right and then click "Editor" on the left.
4. Drag the icon that appears on the right onto a toolbar of your choice. For example, you can drag and drop it onto your Editor toolbar. You can then close the Customize window.
Use the Scale button:
1. Start an edit session. An edit session is required to change the geometry of a feature.
2. Use the Select arrow to select the feature you want to adjust.
3. Click on the Scale button.
4. Hit the "F" key on your keyboard. This opens the scale factor pop-up. Enter in a scale factor to suit your needs, and hit enter to apply the change.
5. When satisfied with your changes, save your changes using the Editor toolbar.
For more information, please see: Scaling a feature.
Let us know if you have any problems!
- Rachel
Rachel Guttmacher
ArcGIS Online Technology Lead
Esri Support Services
