Your process looks right.  The only issue you would run into is if they selected values in more than 1 drop down, your code would produce multiple links.  You can try this method that would eliminate that possibility:

<?php

  $pageName  = "";
  $recordNum = coalesce($record['article'], $record['report'], $record['event'], $record['pages']);
  
  if ($record['article']) {
    $pageName = "articleDetails.php";
  }
  elseif($record['report']) {
    $pageName = "reportDetails.php";
  }
  elseif($record['event']) {
    $pageName = "eventDetails.php";
  }
  else {
    $pageName = "pages.php";
  }
  
?>

<a href = "<?php echo $pageName;?>?num=<?php echo $recordNum;?>" class = "actionButton">Read More</a>

Hope this helps

I've currently got a multi-section "Featured Items" which allows you to create items on the home page, give it a title, image, description, then link to another part of the site.  The same function for "Side Items" and another for "Quick Links" etc.

In each of these section editors, I have the follow fields that allows the user to select where they want that record to link to;

separator: "Choose one of the following items"

pulldown-list: select from database / articles / num / title

pulldown-list: select from database / events / num / title

pulldown-list: select from database / pages / num / title

pulldown-list: select from database / report / num / title

I then use the following to link;

<?php if ($record['article']): ?><a href="articleDetails.php?num=<?php echo $record['article'] ?>" class="actionButton"><?php endif ?>

<?php if ($record['report']): ?><a href="reportDetail.php?num=<?php echo $record['report'] ?>" class="actionButton"><?php endif ?>

<?php if ($record['event']): ?><a href="eventDetails.php?num=<?php echo $record['event'] ?>" class="actionButton"><?php endif ?>

<?php if ($record['pages']): ?><a href="pages.php?num=<?php echo $record['pages'] ?>" class="actionButton"><?php endif ?>

Read More</a>

Is there a better way?