PDF Conversion Router

Route every PDF conversion through a short analysis step before choosing tools or CLI flags.

The goal is not "extract the most text". The goal is:

preserve structure
preserve attachment between labels and values
choose the most faithful output shape
avoid noisy defaults when a better route exists

When to Use

The user wants a PDF converted into another format.
The requested output is .md, .html, .txt, .json, .docx, or structured notes.
The PDF may be scanned, OCR-heavy, table-heavy, slide-based, medical, academic, or multi-column.

Core Rule

Never start with one fixed default pipeline.

Always:

classify the PDF
classify the target output
choose the strongest route for that combination
validate the result on representative sections
if needed, retry with better settings before delivering

Heuristics are starting points, not guarantees.

Do not promote one flag combination into a universal default just because it worked well on one PDF. Prefer document-specific evidence over habit.

Primary Engine Rule

Use opendataloader-pdf as the primary conversion engine for every PDF conversion task by default.

This skill should assume:

opendataloader-pdf is always the first conversion attempt
other tools are used to classify, validate, OCR, inspect, or support cleanup
other extractors are not the default replacement for the main conversion route

Use other tools only for one of these reasons:

quick classification of the PDF
OCR preprocessing before conversion
validation against layout-preserving text
manual repair when the generated output is still noisy
fallback only if opendataloader-pdf cannot produce a usable result

Step 1: Classify the Source PDF

Identify the document class as quickly as possible:

Native digital PDF with selectable text
OCR PDF with noisy text
Image-only/scanned PDF
Slide deck / presentation export
Medical or lab report
Table-heavy business/finance document
Narrative report / letter / article
Mixed layout document with diagrams, tables, and prose

Useful fast checks:

pdfinfo input.pdf
pdftotext -layout input.pdf -

If text is missing or very poor, treat OCR as required.

Document-Type Heuristics

Use these as default starting points:

medical / lab report markdown-with-html + --table-method cluster + --image-output off
slide deck / PowerPoint export markdown-with-html + --image-output off add --table-method cluster only if the default route under-structures important tabular content if tables are visually obvious but missing or badly fused, treat this as a detection problem, not a Markdown formatting problem if the selected route already reconstructs a real table but clips leading characters at column boundaries, treat that as a boundary-splitting defect, not a missing-table failure
narrative / article / letter start with markdown or text use markdown-with-html only if structure clearly matters
table-heavy business / finance PDF start with markdown-with-html add --table-method cluster when rows or columns flatten
scanned / image-heavy PDF OCR first, then convert with opendataloader-pdf
mixed-layout PDF prefer markdown-with-html validate one easy section and one hard section before accepting output

Step 2: Choose the Output Shape

Pick the output that best matches the document and the user's goal.

markdown-with-html Use by default when the user wants Markdown and fidelity matters. Prefer this for tables, medical reports, slides, mixed-layout PDFs, and anything likely to break in pure Markdown.
markdown Use only when clean plain Markdown matters more than layout fidelity.
html Use when visual structure matters more than LLM readability.
text Use for quick linear extraction, narrative documents, or when structure is unimportant.
json Use when downstream machine processing matters more than human readability.
docx Use when the user wants editable office output and layout reconstruction matters.

Step 3: Choose the Extraction Route

For OpenDataLoader CLI

Use OpenDataLoader as the default route.

Preferred defaults:

For Markdown output with fidelity priority: -f markdown-with-html
For medical PDFs: add --table-method cluster
For table-heavy PDFs: add --table-method cluster
For slide decks: start without --table-method cluster add it only after a structure check shows meaningful improvement if a pseudo-table is already collapsed inside one detected row, changing only the Markdown flavor usually will not fix it if the active engine build recovers the pseudo-table structure, prefer fixing residual boundary artifacts before escalating to hybrid/full mode
For conversions where images are not requested: add --image-output off
For slide decks, medical reports, and structure-sensitive PDFs: prefer validating both the command success and the actual rendered structure
For referts/reports where exact values matter: validate key sections after conversion instead of trusting first pass

For medical or lab PDFs

Default route:

opendataloader-pdf -f markdown-with-html --table-method cluster --image-output off

Then verify:

main table headers
attachment of value, unit, and reference range
legends/comments separated from result rows

If a clinical table is flattened, compare against pdftotext -layout before accepting output.

For slide decks

Prefer:

opendataloader-pdf -f markdown-with-html --image-output off

Then check for:

repeated footers
page numbers
diagram pseudo-tables
orphan symbols and chart labels

If CLI output is still poor, do a cleanup pass tuned for slides instead of assuming the raw extract is final. If the slide contains obvious table-like blocks that are not detected as tables at all, prefer a same-engine retry with a stronger route such as hybrid/full mode before jumping to unrelated extractors. If the slide now produces a real table, validate the first column and header boundaries before assuming the table is fully correct.

For scanned PDFs

If the text layer is poor or absent:

run OCR first
then convert the OCR'd PDF with opendataloader-pdf

Prefer conservative reconstruction over aggressive guessing.

Step 4: Validation Gates

Before claiming success, inspect the output for the patterns most likely to break.

For medical PDFs:

values attached to correct exam names
units and reference ranges not merged into neighbors
comments not merged into rows

For slides:

bullets normalized
footers/page numbers removed when they are noise
diagrams not causing crashes
remaining tables readable enough to follow
first column labels not losing their first character at inferred column boundaries
pseudo-table recovery not breaking row grouping or spilling labels into the next column

For table-heavy documents:

no catastrophic row flattening
headers preserved
repeated empty separator rows minimized
sparse or single-column tables not accidentally collapsed into prose
table bodies not fused into a single HTML or Markdown row containing many logical records

For every document class:

check the first representative section, not just the top of the file
check one complex section, not only a simple section
prefer document-level confidence over success on page 1

Red Flags

Treat these as signals that the current output is not ready:

table rows flattened into long prose lines
table header looks correct but the entire body is fused into one row with multi-value cells
labels detached from values
units or reference ranges drifting into adjacent rows
repeated page footers or page numbers
pseudo-tables with mostly empty cells
legitimate sparse tables collapsed into paragraphs
single-column tables flattened because they looked "too simple"
stray symbols, bullets, or OCR fragments
good command exit code but visibly poor structure
page 1 looks fine but a later complex section is broken
switching from markdown to markdown-with-html improves wrapping but does not restore missing row boundaries
a pseudo-table is now emitted as a table, but key labels are clipped at the left edge of cells

Never Trust Page 1

Do not accept a conversion just because the top of the file looks good.

Always validate:

one early section
one structurally difficult section
one section likely to matter most to the user

For medical PDFs, this means checking a real lab table, not just the heading block.

For slide decks, this means checking at least one dense diagram or pseudo-table, not just the title slides.

Step 5: Post-Conversion Repair Pass

Conversion is not finished just because a file was generated.

If the output is structurally correct but still noisy or hard to read, perform a cleanup pass before delivering it.

Use three buckets:

cleanup For noise reduction without changing meaning. Examples:
- repeated footers
- page numbers
- duplicated bullet markers
- stray symbols
- empty separator rows
- trivial one-cell pseudo-tables that should become plain text
Important: do not collapse a table just because it is sparse, narrow, or mostly empty. Preserve legitimate single-column and sparse tables if they still carry table meaning.
structural correction For repairing attachment and readability when the extractor found the right content but the wrong structure. Examples:
- flattened tables
- fused columns
- notes merged into result rows
- legends mixed into measurements
- broken section boundaries
route retry For cases where the problem comes from the wrong extraction path, not from output cleanup.

Always prefer the least invasive repair that produces a faithful, readable result.

Do not leave raw noisy output untouched if it is clearly improvable.

Step 6: Retry Rules

Do one targeted retry if the first route is wrong.

Examples:

Markdown too flat for tables -> switch to markdown-with-html
Table detection weak -> retry with --table-method cluster
Table wrapper exists but body rows are fused -> treat as structural extraction failure; inspect JSON or a structure-preserving view, then retry the route instead of only cleaning Markdown
Table structure is recovered but leading characters are clipped at cell boundaries -> treat as a boundary-splitting defect; prefer tightening the same-engine structure logic over routing to an unrelated extractor
OCR missing text -> OCR first, then reconvert
Slide output noisy but structurally usable -> keep extractor, improve cleanup
Slide pseudo-table not detected -> retry same engine with hybrid/full mode before non-OpenDataLoader fallback

Do not keep blindly retrying many variants. Choose the next attempt based on the failure mode.

Prefer this retry order:

same engine, better flags
same engine, different output shape
same engine plus hybrid/full mode when available
same engine plus cleanup/repair
OCR preprocessing plus same engine
only then consider a non-OpenDataLoader fallback if truly blocked

For --table-method cluster, treat it as a targeted retry or document-specific default, not a universal default. It is often the best choice for medical PDFs, but not automatically for every slide deck or every business document.

Default Preferences

When the user does not specify otherwise:

prefer markdown-with-html over pure markdown
disable images unless the user wants them
prefer --table-method cluster for medical PDFs
consider --table-method cluster for table-heavy PDFs when rows or columns flatten
do not assume --table-method cluster is the best default for slide decks
do not assume markdown-with-html alone fixes fused table rows if the underlying table structure is already wrong
do not assume hybrid/full is still necessary if the active engine now reconstructs the pseudo-table correctly enough
verify the real output, not just the command exit code
keep the original PDF untouched
prefer creating the converted file in a dedicated output folder
prefer giving the user the final chosen output path, not just a command summary

Benchmark Safety Rule

If the work involves changing opendataloader-pdf behavior itself, not just running a conversion:

validate the target real-world PDF
validate at least one difficult public benchmark case if available
avoid cleanup rules that improve one document by degrading sparse or edge-case tables elsewhere
explicitly check for the failure mode where a valid-looking table header is followed by a single fused body row
if fixing a slide pseudo-table, also re-check a previously recovered dense-table case so the new heuristic does not reopen an old regression
distinguish benchmark wins from cosmetic residual defects such as left-edge character clipping inside recovered cells

Wins on one PDF are useful, but they do not justify turning a heuristic into a global default without broader validation.

Limitations

This skill routes and validates conversion work; it does not guarantee that opendataloader-pdf, OCR tools, or PDF utilities are installed in every environment.
Complex PDFs can still require manual structural repair after the best route succeeds.
OCR quality, source scan quality, and malformed PDF internals can limit fidelity no matter which route is chosen.
Visual fidelity is secondary to document fidelity, so exact page layout may not be preserved unless the user explicitly requests it.

Delivery Checklist

Before finishing, make sure you can state:

which opendataloader-pdf route was chosen
whether a retry was needed
whether cleanup or repair was applied
which output file is the recommended final one
any remaining limitations that still affect readability or fidelity

Fidelity Rule

Distinguish between:

document fidelity correct content, correct attachment, correct section structure
visual fidelity preserving the original visual layout as closely as possible

Optimize first for document fidelity.

Do not sacrifice semantic correctness just to imitate the original page visually.

For most conversions, a structurally correct and readable output is better than a visually similar but semantically broken one.

Delivery Rule

Do not deliver raw extractor output without a cleanup and validation pass when fidelity matters.

If the document is complex, say which route was chosen and why.

pdf-conversion-router