If you have an Excel file and you do not want other people to modify when you share with other people, you can save the Excel file as a PDF file with the steps below:
Step 1: Open the Excel file, and click the "File" tab from the ribbon, then click "Print" from the list. After this, come back to the Excel worksheet and you will find the print margin is now available in the file;
Note: This is not to print, but to add the print margin to the Excel.
Step 2: Go over all the pages and make sure there are no tables and images crossing the margin. Also, try to make all columns inside of the margin.
If part of the content is out of the margin, you need to adjust the width of the content to bring them back to the margin;
Step 3: If everything looks fine, click the "File" tab from the ribbon again, and click "Save as" from the left navigation list. This is very similar to save a Word document as the PDF file;
Step 4: Browse to the location where you want to save the PDF file, e.g., Desktop;
Step 5: In the "Save as format" box, select "PDF" from the drop-down list.
Step 6: If you want to open the PDF document after saving, check the box of "Open file after publishing".
Step 7: Click "Save" and you will see the PDF file is open now. Please note that if your Excel worksheet contains tables, the table borders are normally thick after saving as PDF file. Please refer to why borders are thick when saving Excel tables to PDF and fix it if you need to.