Review quiz · Learning

All 38 questions from the ends of the Learning pages, in reading order. Pick an answer and check it: every answer comes with the reason, and a wrong one links back to the page that covers it.

Foundations

The big picture

Q1. A PostScript file is a program you run to get pages. What is a PDF file instead?

A compiled version of the same program

A database of numbered objects with an index

A sequence of page images

An XML document with embedded fonts

Check

Q2. How different is PDF 1.7 (ISO 32000-1) from PDF 1.4 at its core?

A new syntax and object model

The same syntax, but a new imaging model

The same syntax, object model and imaging model, plus later additions

Identical: ISO only renamed it

Check

Q3. A PDF 1.3 reader opens a file that uses transparency. What happens?

It refuses to open the file

It shows a warning and skips the transparent objects

It renders the transparent content correctly

It renders the transparent content as opaque, without a warning

Check

Objects

Q4. Which of these is not a valid PDF number?

.5

-3

1e5

3.14

Check

Q5. A stream has /Filter [/ASCII85Decode /FlateDecode]. In what order does a reader decode it?

ASCII85 first, then Flate

Flate first, then ASCII85

Either order gives the same bytes

Only the last filter applies

Check

Q6. Why may a stream's /Length be an indirect reference such as 7 0 R?

So several streams can share one length

Because lengths over 65535 must be indirect

So that encryption can change it

Because a writer streaming its output doesn't know the length until it has written the data

Check

File anatomy

Q7. What does each in-use entry of a classic cross-reference table store?

The object's byte offset in the file

The object's length in bytes

A hash of the object

The page number the object belongs to

Check

Q8. Where does a reader start when it opens a PDF?

At the %PDF- header

At the end of the file, looking for startxref

At the document catalog

At the first page object

Check

Q9. How does an incremental update change a file?

It rewrites the changed objects in place

It replaces the trailer and nothing else

It appends the changed objects, a new xref section and a trailer whose /Prev points to the old xref

It rewrites the whole file with the changes merged in

Check

The document tree

Q10. How is the document tree laid out in the file?

As nested dictionaries, indented like the tree

Catalog first, then the page tree in order, then the pages

As numbered objects in any order, linked by N 0 R references

In a separate section after the cross-reference table

Check

Q11. Which of these page attributes is not inherited from a /Pages node?

/MediaBox

/Rotate

/Resources

/Contents

Check

Q12. A 1.3 file is edited with an incremental update that uses 1.4 features. Where does the new version number go?

Rewrite the %PDF- header

The /Version entry in the catalog

The trailer's /Info dictionary

A new startxref comment

Check

Drawing a page

Content streams

Q13. In default user space, where is the origin and what is one unit?

Top-left, 1 pixel

Bottom-left, 1/72 inch

Top-left, 1/72 inch

Center, 1 mm

Check

Q14. What does 0 0 1 RG set?

The fill color, to blue

The stroke color, to blue

Both stroke and fill, to blue

The stroke color, to red

Check

Q15. An image is painted with /Im0 Do. What decides its size on the page?

Its /Width and /Height, read as points

The page's /MediaBox

The current transformation matrix: images always paint into the unit square

The image's own /BBox

Check

Graphics state

Q16. Which of these is not saved and restored by q and Q?

The clipping path

The text matrix

The fill color

The font set with Tf

Check

Q17. A form XObject's content stream never sets a fill color. What color do its fills come out in?

Black, the initial value

Whatever fill color was current at its Do

The color named in its /Resources

None: unset fills aren't painted

Check

Q18. Which of these can only be set through an ExtGState dictionary and gs?

Line width

Fill color

Font and size

Overprint

Check

Text and fonts

Q19. Copy-paste from a PDF gives garbage characters. What is most likely missing?

A /ToUnicode CMap on the font

An XMP metadata stream

The /MediaBox

A /StructTreeRoot

Check

Q20. Which font type do modern generators use for arbitrary Unicode text?

Type1

TrueType

Type3

Type0

Check

Q21. An OCR'd scan has searchable text over the page image. Which text rendering mode draws that text?

0, fill

1, stroke

3, invisible

7, add to clipping path

Check

Transparency

Q22. Which ExtGState key sets the opacity of fills?

/CA

/ca

/BM

/SMask

Check

Q23. What does an isolated transparency group (/I true) composite its contents against?

A transparent backdrop

Whatever is already on the page beneath it

The group's first element

White

Check

Q24. Why do PDF/A-1 and PDF/X-1a forbid transparency?

They are based on PDF 1.3, before transparency

They chose the opaque subset of PDF 1.4 for predictable output

Transparency invalidates digital signatures

Printers can't reproduce transparency

Check

Beyond the page

Encryption and signatures

Q25. In an encrypted PDF, what is encrypted?

Everything after the header

Strings and streams; dictionaries, names and numbers stay in the clear

Only the page content streams

Only the document information dictionary

Check

Q26. An encrypted file's /P forbids printing. What stops someone who can open it from printing it?

Only the reader choosing to honor /P

The encryption itself

The owner password, which is needed to decrypt the content

A digital signature over /P

Check

Q27. What does a signature's /ByteRange cover?

The page content streams

The objects changed since the last save

The signature field's widget annotation

The whole file except the hole holding the signature value in /Contents

Check

Interactive features

Q28. Why should an annotation have an appearance stream (/AP)?

So that it can be clicked

So that it renders the same in every reader

So that text extraction includes it

Because links don't work without one

Check

Q29. Which of these is not an action type?

GoTo

URI

Widget

JavaScript

Check

Tagged PDF and metadata

Q30. What in the catalog declares that a file follows Tagged PDF conventions?

/StructTreeRoot

/MarkInfo << /Marked true >>

/Lang

/Metadata

Check

Q31. In a structure element, what does /K 0 mean?

Knockout is off

The element has no children

The content marked /MCID 0 on the element's page (/Pg)

The element's first child in the parent tree

Check

Q32. How does a viewer find which structure element owns the text under the cursor?

It searches the structure tree from the root

From the page's /StructParents, through the /ParentTree, to the entry for that MCID

Through the font's /ToUnicode CMap

From the marked-content tag before BDC

Check

Q33. Every page has a running page number. How should a tagged PDF mark it?

As a /P structure element

With /ActualText

As an /Artifact in the content stream

Leave it unmarked

Check

Q34. Which kind of metadata was added in PDF 1.4 and is required by PDF/A?

The document information dictionary (/Info)

An XMP metadata stream (/Metadata)

The /MarkInfo dictionary

The trailer's /ID

Check

Wrapping up

What changed from 1.4 to 1.7

Q35. Which version introduced object streams and cross-reference streams?

1.4

1.5

1.6

1.7

Check

Q36. Which of these may be stored inside an object stream?

A page content stream

The encryption dictionary

A page dictionary

The cross-reference stream

Check

Q37. In a cross-reference stream, what does a type 2 entry say about an object?

It is free

It is at a byte offset in the file

It is inside an object stream: which one, and its index there

It is encrypted with a crypt filter

Check

Q38. How many content-stream operators did PDF 1.5, 1.6 and 1.7 add between them?

None

Check

Reset

38 questions

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.