Download Wikipedia article as a .pdf, with program not shown correctly

All you have to do is click the Edit button at the top of an article's page. In the page that you see afterward, you can make your changes and then save them.

You won't be able to edit some Wikipedia articles, however - instead of an Edit button, such protected articles will show a View Source button.

Also, when editing an article, it is recommended that you click Preview before you save your changes. This way, you can make sure that your changes were made as you intended.

For editing, you don't even have to log in. However, if you don't log in, there are a few disadvantages:

• Your IP address is posted and visible to the whole world - can lead to security issues
• You may lose some credibility

Before editing, I recommend you read some of Wikipedia's guidelines, so that you understand how Wikipedia works and how articles are supposed to be.

One last thing - it may be hard to get used to how formatting works on Wikipedia. That's why they wrote a cheatsheet for editors.

First, let me say that I don't think doing this is a good idea. Category description pages on Wikipedia shouldn't contain article text, that's not what they're for. If you want to do this, make sure there is a consensus to do it. For some more information, see Creating category pages.

If you're sure you want to do this, I think the only way (ignoring custom or some existing extension) is to use template transclusion. This can be done two ways:

If you know that you'll always want only this specific section, you can enclose it in <onlyinclude> tag. Then you can transclude the article to the category page (e.g. {{:Pollution in India}}) and only this section will show up.

But if you want to transclude different sections of the same article to different categories, that won't work (unless you also added some {{#if}}s to the article, which I don't think is a good idea). What you can do then is to split the article into multiple parts, each within its own template. So, the text of the section Water pollution might be in Template:Pollution in India/Water. Then you can transclude that template to both the article and the category (using {{Pollution in India/Water}}).