SaveAsPdfUa 方法

SaveAsPdfUa performs the regular SaveAs first, then layers an incremental update on top of the saved bytes that promotes the file to a PDF/UA-1 archive (ISO 14289-1:2014). The post-processing injects four classes of markers into the saved stream:

• An XMP metadata stream that declares PDF/UA identification (pdfuaid:part = 1) plus the matching pdfaExtension:schemas description, the mandatory dc:title entry (ISO 14289-1 §7.1), and bridged Info-dictionary fields (Author, Subject, Producer, Keywords, CreationDate, ModDate, etc.).
• Catalog /MarkInfo << /Marked true /Suspects false >> when the source catalog has no /MarkInfo entry (§7.1).
• Catalog /ViewerPreferences << /DisplayDocTitle true >> when the source has no /ViewerPreferences entry (§7.1).
• Catalog /Lang (xx) when the source has no /Lang and Options.Language supplies a BCP 47 tag (§7.2). The trailer also gets an /ID array (reused from FPDF_GetFileIdentifier when available, otherwise derived deterministically from the source bytes).

The output stays byte-identical to the base SaveAs result up to the end of the original PDF; only the incremental update is appended Existing readers that don't understand PDF/UA still render the file exactly as the regular SaveAs would. The two overloads differ only in how the configuration is passed in: the file-name-only form uses TPdfUaSaveOptions.Default with auto-population from FPDF_GetMetaText / FPDF_GetFileIdentifier / FPDFCatalog_GetLanguage, while the TPdfUaSaveOptions form lets the caller override Title, Author, Subject, Keywords, Creator, Producer, CreationDate, ModDate, Language, DocumentId, InstanceId, and the pdfuaid Part / Amd / Corr identifiers.

Returns True on success. Returns False if the base SaveAs failed or if the incremental update could not be attached (PDF too short, invalid trailer, encrypted source).

• SaveAsPdfUa attaches the file-format markers required by ISO 14289-1 — it does not generate a structure tree, embed missing fonts, add Alt text to figures, or otherwise alter page content. Authoring a tagged document (StructTreeRoot, Figure /Alt, table /TH /Scope, etc.) is still the caller's responsibility. Use ValidatePdfUa to surface the absence of those content-level requirements.
• The injection is purely additive: if the source already carries /MarkInfo, /ViewerPreferences, or /Lang, those entries are preserved and SaveAsPdfUa does not overwrite them. /Metadata is always replaced with the new PDF/UA XMP.
• Encrypted documents cannot be saved as PDF/UA. Call SaveAs(..., saRemoveSecurity) first if needed.
• Works on every platform supported by PDFiumPas because the post-processing is implemented in Pascal and does not depend on PDFium DLL exports beyond the metadata readers.