If you want to add some custom/local changes in article_info.php, you need to add a custom php file with name custom_tpl_article_info.php in themes/functions/ folder where you can add the new changes and define those to a template variable. Also you should place that variable in themes/{Current theme}/articles/article_info.tpl

Here is the template variables used for articles info page. 

1) {$articles_name} - To display the name of the article

2) {$authers_link} - To display the website link of the article author

3) {$articles_image} - To display the article image if added

4) {$articles_image_caption} - To display the image caption if added

5) {$articles_description} - To diplay the article content

6) {$articles_url} - To display the URL of the article if added

7) {$articles_date} - To display the article creation date

8) {$articles_reviews_count} - To display the count of the reviews added for this article

9) {$articles_reviews_button} - To display the button for writing the review for the article

10){$articles_tell_friend_heading} - To display the heading for the tell a friend section

11){$articles_tell_friend} - To display the textbox for entering the email id and button for sending the mail
12){$articles_xsell} - To display the products associated with this article if added from Settings -> B Runtime -> Article Manager -> Cross-Sell articles.