Pdfium Impl Document Features

pdfium-impl-document-features

Work with the four document-level feature collections in pdfium-render: metadata, embedded attachments, permission flags, and digital signatures. Each hangs off a PdfDocument handle.

Scope: document-level features. For page content see pdfium-syntax-pages and pdfium-impl-page-objects-edit. For bookmarks, links, and destinations see pdfium-impl-navigation. For saving edits see pdfium-impl-saving.

Default API surface is 0.9.x. All four collections predate 0.8.x and are fully available in both the 0.8.x and 0.9.x lines.

The one rule that dominates this area

Three of the four collections are READ-ONLY. Only attachments can be written.

ONLY attachments has a _mut() accessor. There is no metadata_mut(), permissions_mut(), or signatures_mut(). pdfium-render does not write metadata, does not change permissions, and does not create signatures.

Quick Reference

Metadata

PdfDocumentMetadataTagType has exactly eight variants: Title, Author, Subject, Keywords, Creator, Producer, CreationDate, ModificationDate. There is NO Trapped variant. get() returns None when a tag is absent.

Attachments

Permissions

Every getter returns Result<bool, PdfiumError> (or Result<PdfSecurityHandlerRevision, PdfiumError> for the revision).

security_handler_revision    can_print_high_quality
can_print_only_low_quality   can_assemble_document
can_modify_document_content  can_extract_text_and_graphics
can_fill_existing_interactive_form_fields
can_create_new_interactive_form_fields
can_add_or_modify_text_annotations

PdfSecurityHandlerRevision has four variants: Unprotected, Revision2, Revision3, Revision4.

Signatures

PdfSignatureModificationDetectionPermission has three variants: Mdp1, Mdp2, Mdp3.

Full signatures and version annotations: references/methods.md.

Patterns

Condensed patterns below. Complete runnable code is in references/examples.md.

Pattern 1: Read metadata

let document = pdfium.load_pdf_from_file("doc.pdf", None)?;
let metadata = document.metadata();
for tag in metadata.iter() {
    println!("{:?} = {}", tag.tag_type(), tag.value());
}
if let Some(author) = metadata.get(PdfDocumentMetadataTagType::Author) {
    println!("Author: {}", author.value());
}

CreationDate and ModificationDate values are raw, UNPARSED PDF date strings in D:YYYYMMDDHHmmSS format. Parse them yourself if a typed date is needed.

Pattern 2: Extract attachments

for attachment in document.attachments().iter() {
    let data = attachment.save_to_bytes()?; // Vec<u8> of the file content
    println!("{}: {} bytes", attachment.name(), data.len());
}

PdfAttachment has no bytes() accessor. Extraction goes through save_to_bytes() (memory) or save_to_file() (disk).

Pattern 3: Create an attachment

let mut document = pdfium.load_pdf_from_file("doc.pdf", None)?;
document
    .attachments_mut()
    .create_attachment_from_bytes("notes.txt", b"payload")?;
document.save_to_file("doc-with-attachment.pdf")?; // mandatory

Creation needs &mut PdfDocument via attachments_mut(). The new attachment lives in memory until the document is saved. See pdfium-impl-saving.

Pattern 4: Delete attachments

let count = document.attachments().len();
for index in (0..count).rev() { // downward: deleting shifts later indices
    document.attachments_mut().delete_at_index(index)?;
}
document.save_to_file("doc-cleaned.pdf")?;

delete_at_index is the ONLY deletion method. Deleting shifts every later index down by one, so deleting multiple attachments ALWAYS goes from the highest index downward.

Pattern 5: Query permissions

let perms = document.permissions();
println!("print HQ:       {:?}", perms.can_print_high_quality());
println!("modify content: {:?}", perms.can_modify_document_content());

Pattern 6: Read signatures

for signature in document.signatures().iter() {
    println!("reason: {:?}, signed: {:?}",
        signature.reason(), signature.signing_date());
}

PdfSignatures is read-only. There is no signature-creation API and no cryptographic verification. The signer identity lives inside the bytes() PKCS#7 blob, which a separate cryptography crate must parse.

Permission flags are reported, not enforced

PdfPermissions getters REPORT the flags stored in the document. They do NOT gate any pdfium-render operation. can_modify_document_content() returning false does not stop attachments_mut(), annotations_mut(), or any edit call. To respect a permission, check the flag and branch in your own code BEFORE calling an edit method.

Common mistakes

Each mistake is explained with root cause and fix in references/anti-patterns.md.

Reference files

• references/methods.md: complete API signatures with version annotations.
• references/examples.md: working, verified Rust examples.
• references/anti-patterns.md: real failures, why they fail, and the fix.

Related skills

• pdfium-syntax-document-loading: loading the document these features hang off.
• pdfium-impl-navigation: bookmarks, links, and destinations.
• pdfium-impl-saving: persisting attachment create and delete changes.
• pdfium-impl-form-fields: interactive form fields (a separate feature).
• pdfium-errors-runtime: handling PdfiumError from these calls.