Although the file may look absolutely fine offline, when uploaded to YUDU it shows lines between images and generally across the page - what can cause this?
The main cause of the issue is due to transparencies that are not supported by YUDU. The process goes that when a user attempts to flatten transparencies using a suite such as Adobe Acrobat, images are raised and replaced removing the transparencies, however they are not placed EXACTLY as they were before - instead there are small lines between them. This is accentuated on the Publisher system and will need to be removed.
In order to remove these, one can amend the pre-production PDF to remove transparency elements (not simply flattening them). Alternatively if the pre-production PDF is not available, flattening the entire page will work fine, however there may be a slight reduction in quality and removal of plain text (this is used for the search and automatic linking on YUDU).
We recommend following the File Specifications Guide whilst producing the PDF in order to achieve the optimum performance, quality and compatibility possible.