I have intermittently run into this issue as well, but I have found that after the “http error” message appears to stop the upload, I can close the file upload dialog, go to something else on the admin menu and then go back to the Media Library tab – and viola! the pdf file then appears.
I have taken to gathering pdf files into one folder on my laptop, doing a bulk upload, and walk away for a while. When I get back, I close out all the errors and close the upload, open a random page, close it, and then go back to the media library to attach the documents to their respective pages.
It would be nice to get a real fix, but in the meantime, this is how I work around the http error.
Dave
