If your attachments are too large to upload to "My attachments" there are several ways of reducing the file size.
It's possible to compress PDF-files in order to reduce the file size without losing quality. This is particulary useful in PDFs of publications, scanned documents and files containing pictures and graphics. When creating a new PDF from applications like Microsoft Word and Adobe Acrobat you can adjust the quality and file size when saving the PDF file to your hard drive.
If you have an existing PDF you wish to compress we can recommend free services like SmallPDF.
If you have large image files you can either reduce the file size in an image editing application, or use SmallPDF to convert these to PDF files.
It can be useful to save text documents in Microsoft Word-format (.doc or .docx) as PDF-files and follow the instructions above to make the file size as small as possible.
If your attachments still exceeds the storage limit you can try to upload them to external services like Dropbox or Google Disk. Read more here.