If you have issues with particular files in either PDF Viewer for iOS or Android, it often helps a lot to identify the root cause of these issues when you share the files with us.
The best way to do this is to upload these files to a cloud service that has the ability to share files, like Dropbox or Google Drive. When you upload these files there, you can then create a share link and send this link when talking to our support.
You can also upload files directly by contacting our support from our website (https://pdfviewer.io > Support). There you have the option to attach files of up to 40MB to a support request. If you are communicating with us via email, another option is to send the file directly by email, if the file you are having issues with is small (a couple megabytes).
If the file you are trying to send us is larger than 40MB and you don't have access to a cloud provider, please ask us in support. We can generate you a link to a cloud provider where you can then upload a single file.