For my first diary in Oxdown, I wanted to post the following image, but it took me a while to get it to show up:
To make the image, I first used the "snipping" tool in Windows to grab a section of the pdf file I wanted to quote. The pdf had been saved in the format that doesn’t allow copying sections of the text. I saved the snippet as a jpg on my desktop and then uploaded it to flickr. However, when I tried to paste the image into my Oxdown diary, I first tried copying the url from the page obtained by clicking on the photo on my flickr home page. Instead of seeing the image in preview mode, all I saw was the alternate text I had supplied at the prompt. Instead, what works is to right-click on the image on its flickr page and select the windows option that allows you to copy the image location. Pasting that into the dialog for embedding the image works just fine.
Hope this helps. Happy diary-posting!
PS: The windows "snipping" tool is useful for grabbing a portion of any web page, not just a pdf.