I had the following experience filing a provisional with landscape drawings. Before continuing, I should note that I converted the drawings to bitonal formal (by converting to TIFF and back to pdf). They were standard Letter size with a landscape orientation.
When I uploaded the drawings in Patent Center, it displayed an error saying "Warning: The page size in the PDF is too large. The pages should be 8.5 x 11 or A4. If this PDF is submitted, the pages will be resized." I double checked the drawings and they were standard Letter size pages. I shrugged it off and finished the filing.
I checked later and four of the five pages of drawings were blank. The only page that showed up was badly mangled. Rather than rotate the page, Patent Center tried to change the size of the page so it had the same orientation but was reduced to fit in a standard Letter size portrait orientation.
I think technically, 8.5 x 11 is different than 11 x 8.5. However, many users do not distinguish page size in this way. Many users think in terms of something being standard Letter size (8.5 x 11) but in portrait or landscape orientation. In the minds of many users, a Letter size document is the same size regardless of the orientation.
In view of this situation, I would suggest modifying the filing process in one of the following ways:
Option 1—Patent Center rotates landscape pages to portrait as part of filing process. Patent Center checks the filed documents to see if the pages are an acceptable size (A4 or 8.5 x 11) but have a landscape orientation. If so, the user is shown the following message (or a similar message): "Warning: one or more of the pages in the PDF file appears to have a landscape orientation. The pages should have a portrait orientation that is 8.5 x 11 or A4. If the PDF is submitted, the landscape-oriented pages will be resized."
Option 2—Patent Center provides a more informative warning message. Patent Center checks the filed documents to see if they are the correct size. If they are not, Patent Center displays the following message (or a similar message): "Warning: The page size in the pdf file is incorrect. The pages should have a portrait orientation that is 8.5 x 11 or A4. If the pdf file is submitted, the pages will be resized."
I would prefer the first option, but I understand it will require more effort on your end to rotates pages, create different warning messages based on the drawing problems present (i.e., the warning message will need to be different than what I suggested if one page is 8 x 10), etc. Even if the first option is not feasible, the second option can easily be implemented. It at least informs the user that the pages must have a portrait orientation.
Please change Patent Center in this manner to make it more user friendly.