There are three methods you can use. To place a line at the bottom of each page, go to insert->line and draw a line across the bottom of the page footer.
If you need to place conditions on its appearance, then select insert text box, and place it in the page footer, stretch it to fit the width of the page, then select the text box, right click on it, select change border and select a single line for "top." Add any conditional criteria by clicking on E2 and creating a formula.
If you want the line to fall exactly at the end of the last record on the last page, not on the bottom, then put the text box in the details section, stretching it around all fields. Select the type of line for "bottom" and then click on E2 and enter a formula:
if onlastrecord or
recordnumber = 25 then crSingleLine else crNoLine
This assumes you have 25 records per page, so change the 25 to reflect the actual number. You can insert {recordnumber} from the field explorer->special fields into the details field just to see. It appears that this will work since you won't have any group headers or footers which could change the number of records per page.
If you are suppressing any records or doing a record select you would need to substitute a running total for {recordnumber} in the formula, where the running total counts an ID field that appears in every record, evaluate based on a formula that excludes those records that you are already excluding through suppressions or a group select, and reset never.
-LB