The process that is used to apply the journal information to your paper requires that the PDF file meets the PDF/A-1 standard, or essentially equivalently version 1.4. This is because the method used to compress the data in the file changed from version 1.5 onwards, and the open-source program that is used to modify the file is not able to process the later compression method. We attempt to convert PDF files submitted with pdf version greater than 1.4 to 1.4, but this is not guaranteed to be completely reliable. You will be warned if this conversion has happened and you should check the converted paper particularly carefully. Note that the PDF/A has been augmented to include later versions, and PDF/A-2 or above should not be used.
We expect that all common word processing programs will be able to produce PDF/A-1 output, we use MS Word 2007 for which the steps necessary are:
For more recent versions of Word we expect that a similar option will be available.
We also use the Open-Source LibreOffice, in which case (for version 6.2):
If you have difficulty in producing a PDF file with a suitable version, the web page at Docupub supports free online conversion of any PDF version to any other. It can also convert many other formats, including Word documents, to PDF.