AS ISO 24517.1:2017 Document management – Engineering document format using PDF
18.3 Direct objects in the encryption dictionary
The values of all entries of Tables 3.18, 3.19, 3.21, 3.22, and 3.24 in PDF Reference whose types are string, array, or dictionary shall be direct.
This removes any ambiguity regarding whether strings in subdictionaries or subarrays of the encryption dictionary require being direct. All strings, dictionaries, and arrays in the encryption dictionary that are defined within PDF Reference, no matter how deeply nested, shall be direct. This part of ISO 24517 cannot impose such restrictions on the entries defined by security handlers other than those defined in PDF Reference, but it is important to note that any such strings used for decryption are required to be direct to avoid circular dependencies in reading the encryption dictionary when the document is opened.
18.4 User access permissions
A PDF/E-1 conforming reader shall restrict user access to an encrypted PDF file according to the permissions contained in the file.
19.1 General
PDF Reference defines a variety of signature features. However, some of them rely on algorithms for computing digest values that are not fully documented. PDF/E restricts the use of signature features to those that are completely and unambiguously specified. Restrictions on the digital signature features that may appear in a PDF/E-1 file are given 19.2 to 19.5. The behaviour of PDF/E-1 conforming readers with respect to digital signatures are defined in 19.6 to 19.10.
19.2 Declaring the presence of signatures
A PDF/E-1 conforming file that contains signature fields shall have a SigFlags entry in the interactive form dictionary (PDF Reference, section 8.6.1). The low-order bit of this entry shall be 1. If the document contains no signature fields, the SigFlags entry shall either be absent or the low order bit shall be 0.
NOTE This subclause guarantees that the SigFlags entry accurately reflect the status of the document with respect to the presence of signature fields.