What changed from 1.4 to 1.7 · Learning

Three Adobe releases, then standardization.

None of them added a content-stream operator. The newest, sh, came in PDF 1.3, so 1.4 and 1.7 have exactly the same 73 operators: everything new is in dictionaries, filters and file structure.

PDF 1.5 (2003): compact files and layers

Object streams

Many small non-stream objects packed into one compressed stream. Before 1.5, dictionaries could not be compressed at all, only stream data. This often shrinks files by 20–50%.

7 0 obj
<< /Type /ObjStm /N 3 /First 18 /Filter /FlateDecode /Length … >>
stream
% decompressed: N pairs of "objnum offset", then the objects themselves
1 0 2 40 3 92
<< /Type /Catalog /Pages 2 0 R >> << /Type /Pages … >> << /Type /Page … >>
endstream
endobj

Cannot go in an object stream: streams, objects with generation ≠ 0, the encryption dictionary, the xref stream itself, and in linearized files the linearization dictionary and objects needed for the first page.

Cross-reference streams

The text xref table and trailer are replaced by a /Type /XRef stream whose dictionary is the trailer. Each entry has three binary fields with widths given by /W:

8 0 obj
<< /Type /XRef /Size 9 /W [1 2 1] /Root 1 0 R /Filter /FlateDecode /Length … >>
stream
…binary rows: [type][field2][field3]…
endstream
endobj
startxref
1234
%%EOF

Type	Field 2	Field 3
`0` free	next free object	generation
`1` in use, uncompressed	byte offset	generation
`2` in use, in an object stream	object number of the ObjStm	index within it

Hybrid-reference files keep a classic xref table and add /XRefStm to the trailer, so 1.4 readers still work while 1.5 readers also find the compressed objects.

1.7 §7.5.7 Object streams1.7 §7.5.8 Xref streams

Also in 1.5

Optional content (layers): /OCProperties in the catalog, OCG dictionaries, and content wrapped in /OC /oc1 BDC … EMC. 1.7 §8.11
JPXDecode (JPEG 2000), Crypt filters, and security handler /V 4 with crypt filters.
/XFA in the AcroForm dictionary; certification (DocMDP) and usage-rights signatures.

PDF 1.6 (2004): AES, OpenType, 3D

AES-128 via the /AESV2 crypt filter method (with /V 4 /R 4).
OpenType font programs: /FontFile3 with /Subtype /OpenType.
3D annotations with U3D streams. 1.7 §13.6
NChannel DeviceN color, /UserUnit on pages, measurement dictionaries.
More embedded-file and attachment features.

Adobe later published errata and a blend-modes addendum for this edition.

PDF 1.7 (2006, ISO 2008): portfolios and standardization

Portable collections (PDF portfolios): a /Collection dictionary in the catalog presents embedded files as the main content. 1.7 §12.3.5
Document requirements (/Requirements) to state which reader features the file needs. 1.7 §12.10
Extensions dictionary (/Extensions with /BaseVersion and /ExtensionLevel), how Adobe later layered AES-256 and other "1.7 extension level 3/8" features on top without changing the version number. 1.7 §7.12
ISO 32000-1:2008: same technical content as Adobe's 6th edition, rewritten in ISO style with normative shall/should/may. Adobe granted patent rights for conforming implementations.

Adobe's 1.7 errata is for Adobe's PDF Reference 6th edition, not for ISO 32000-1. Section numbers differ between the two.

Chapter mapping: 1.4 → 1.7

Topic	PDF Reference 1.4	ISO 32000-1
Syntax	ch. 3	§7
Graphics	ch. 4	§8
Text	ch. 5	§9
Rendering	ch. 6	§10
Transparency	ch. 7	§11
Interactive features	ch. 8 (incl. sounds and movies)	§12, with multimedia split into §13
Document interchange	ch. 9	§14
Operators, limits, encodings, linearization, examples, compatibility	App. A, C, D, F, G, H	Annex A, C, D, F, H, I

Rule of thumb: 1.4 chapter N ≈ 1.7 section N + 4.

Section references such as 1.4 §3.4 1.7 §7.5 are to the Adobe PDF Reference, third edition (PDF 1.4) and ISO 32000-1:2008 (PDF 1.7). Where to get them: PDF specifications.