Question: Our client has several specification sheets in pdf format for many of their products. What is the best or easiest way for them to add a downloadable PDF to each product page. (Some PDFs fit many products).

UPDATE: I found a very useful extension for this <http://amasty.com/product-attachments.html>

Answer: 
A simple way to do this, without much programming, is to take advantage of magento's product attributes. It's very simple to do the following -

1. add a product attribute called "spec\_sheets" and allow that attribute to used on the front end. Then add that attribute to the appropriate product attribute sets.
2. have your client FTP the pdf files to a directory under your magento install - say media/specs.
3. edit the product(s) where the spec sheets should be shown and enter the pdf file names.
4. Update the product view template to detect if the attribute has a value by getting it's value, $\_product->getSpecSheet(). If a file exists in media/specs directory with the same name as the attribute, display a link to the PDF on the product page.

If there are more than 1 PDF per product, then you can have the admin enter the filenames in a comma separated list and then use php to parse out the individual filenames.
I've got a better way.  

Install this extension: [Etatva Extension](http://www.magentocommerce.com/magento-connect/product-file-attachment-by-etatvasoft.html)

After installing, add this line to view.phtml. 

```
echo $this->getLayout()->createBlock('files/product_view')->setTemplate('files/files.phtml')->toHtml();  

```

Save it, clear cache, log out, re log in. Go to `System>>Configuration`, you should see that extension in left panel. Play with settings so that pdf files can be uploaded in backend.  

Then add a new product, upload pdf. Then add a custom attribute, make it visible in front end. In backend, use an anchor tag like this for that custom attribute. 

```
<a href="linkwherecustompdfsare stored" alt="pdfdownloader">PDF Downloader</a>  

```

Save it, refresh front end and Voila!!  

You should see a link in front end, clicking on it will download the pdf.  

Tested and verified in Magento CE 1.9.0.1 :)