Yes, you can uniformly scale all worksheets at once in page set-up in Excel. Here's how:

1. Open your Excel file with multiple worksheets.
2. Click on the first worksheet tab at the bottom of the screen.
3. Go to the Page Layout tab in the ribbon at the top of the screen.
4. Click on the small arrow in the bottom right corner of the Page Setup group to open the Page Setup dialog box.
5. In the Page Setup dialog box, go to the Scaling section and select the desired scaling option (e.g. Fit to: 1 page wide by 1 page tall).
6. Click OK to apply the scaling to the current worksheet.
7. Right-click on the next worksheet tab and select Select All Sheets.
8. Repeat steps 3-6 to apply the same scaling to all selected worksheets at once.

By selecting all sheets in step 7, you can apply the same page set-up settings to all worksheets in your file at once, saving you time and effort.