Here's a Securities and Exchange Commission (SEC) filing we don't talk much about at Fool HQ: the S-3, which is used when companies and major stockholders intend to sell shares on the open market. This particular form was in the news this week when shares of upscale women's apparel retailer Cache (NASDAQ:CACH) fell Tuesday on heavy volume following just such a filing.

According to Cache's S-3, available on the SEC's website, some 2 million shares of Cache will hit the market soon, increasing the float and perhaps trading volatility. (Another 300,000 could follow if there's heavy demand.) What's worse -- for regular investors, anyway -- is that only 200,000 of these shares are being sold by the company (the rest come from large shareholders), meaning relatively little of the proceeds will go into Cache's coffers.

But while Cache could certainly use another $4 million or so on its balance sheet, it doesn't really need the money: It's profitable, growing, and generating free cash flow. Meanwhile, the main beneficiaries of the planned sale -- besides the underwriters, natch -- are Directors Andrew and (his father) Joseph Saul and related parties. Both Andrew and Joseph Saul have been directors since 1986, and Andrew was chairman between 1993 and 2000.

We tend not to get overly excited when corporate insiders sell shares; as any investor knows, there are just too many types of reasons to sell, from the ominous to the painfully mundane. (Insider buying is far more interesting.) Heck, Cache's stock has been strong these past 12 months and the Sauls may simply be taking profits. And some of the proceeds, actually, are slated for charity.

Even so, it's worth knowing who's doing what -- especially in cases like these, where Cache's executive and director ownership stands to drop from more than 37% to closer to 23% following the sales. Investigating news "concealed" in S-3 and other filings -- information like this often can't be found in press releases -- is a good use of any investor's time.

A side note to Cache's investor relations department: When I clicked on the "SEC filings" link from the company's website, I got a page from the SEC's website that simply searches the filing database for filings with the word "Cache" in them -- including plenty unconnected to Cache Inc., such as Cache Capital USA and Abraxas Petroleum. Is hosting the documents on the company's own website really that difficult? Even just changing the search to "Cache Inc." improves the results.

Dave Marino-Nachison can be reached at dmarnach@fool.com.