pdf-skill

name pdf-skill description All-in-one PDF read / write / convert / OCR. Trigger scenarios: summarize a PDF, extract text or tables, fill an AcroForm, render pages as images, merge, split, add a watermark, rotate, encrypt/decrypt, create a new PDF (invoice / report / receipt), convert between PDF and docx/md/txt. Typical phrasings: "summarize this PDF", "fill out this PDF form", "merge these PDFs", "add a watermark to the PDF", "convert PDF to Word", "OCR this scan", "show me what page 3 of the PDF looks like". Load this skill whenever the user mentions a .pdf file, needs to produce a PDF, or wants to make any change to a PDF. PDF Skill Read with PdfInspect ; all write / modify / create operations use JsSandbox to run Node scripts via pdf-lib / pdfkit / pdf-parse and similar pre-installed libraries; format conversion uses DocConvert ; scanned PDFs go through CloudImageUnderstand . Tool List Tool Responsibility Read-only PdfInspect Read: summary / text / tables / form-fields / form-structure / images / annotations / render Yes JsSandbox All write operations : create new PDF, merge, watermark, rotate, fill forms, decrypt… implemented with pdf-lib / pdfkit code No DocConvert Format conversion: pdf ↔ docx / html / md / txt / xlsx No CloudImageUnderstand OCR entry point for scanned PDFs (cloud, consumes credits) No Loading (two steps, both required) : LoadSkill pdf-skill — only pulls this skill doc into context. ToolSearch(query: "select:PdfInspect,JsSandbox,DocConvert") — activates the tool schemas. Read on a .pdf gives only a lightweight summary; any analysis / summarization / fill / edit / convert / OCR of a PDF must go through PdfInspect + JsSandbox . 1. Read: PdfInspect is the only entry point When you don't know what the PDF looks like, run summary first: PdfInspect { action: "summary", filePath: "…" } Returns pageCount / fileSize / characterCount / hasForm / encryption / textType . Branch on textType : textType Next step extractable PdfInspect(text) — direct full-text extraction scanned / cid-encoded PdfInspect(render, pageRange) → CloudImageUnderstand on each PNG for OCR isEncrypted: true Decrypt with JsSandbox + pdf-lib , or call PdfInspect(password) Large PDFs must pass pageRange (e.g. "1-5" ), otherwise output will be truncated. AcroForm forms: call PdfInspect(form-fields) to get checkedValue / radioOptions before filling. 2. Write: JsSandbox + pdf-lib / pdfkit Prefer pdf-lib (edit existing PDFs / merge / watermark / rotate / fill forms / decrypt); use pdfkit from scratch when you need complex layouts (vector + text + images). 2.1 Demo: Create an invoice PDF from scratch ( pdfkit ) import PDFDocument from 'pdfkit' import fs from 'node:fs' const doc = new PDFDocument ({ size : 'A4' , margin : 48 }) doc. pipe (fs. createWriteStream ( 'invoice.pdf' )) doc. fontSize ( 22 ). text ( 'INVOICE' , { align : 'right' }) doc. moveDown () doc. fontSize ( 10 ). text ( 'Acme Corp' , { align : 'right' }) doc. text ( 'Invoice #2026-042 Date: 2026-04-20' , { align : 'right' }) doc. moveDown () // Simple table const rows = [ [ 'Widget' , 1 , 50.00 ], [ 'Gadget' , 2 , 30.00 ], ] doc. fontSize ( 12 ). text ( 'Description Qty Unit Total' ) doc. moveTo ( 48 , doc. y ). lineTo ( 547 , doc. y ). stroke () let total = 0 for ( const [name, qty, unit] of rows) { const line = qty * unit total += line doc. text ( ` ${name.padEnd( 14 )} ${qty} $ ${unit.toFixed( 2 )} $ ${line.toFixed( 2 )} ` ) } doc. moveDown (). fontSize ( 14 ). text ( `Total: $ ${total.toFixed( 2 )} ` , { align : 'right' }) doc. end () await new Promise ( r => doc. on ( 'end' , r)) console . log ( 'invoice.pdf written' ) CJK note : pdfkit's default fonts have no CJK glyphs. For Chinese output, call doc.registerFont('cn', '/path/to/NotoSansCJK.ttf') first, then doc.font('cn') . System fallback fonts are not guaranteed to cover CJK. 2.2 Demo: Add a CONFIDENTIAL watermark to an existing PDF ( pdf-lib ) import { PDFDocument , rgb, degrees, StandardFonts } from 'pdf-lib' import fs from 'node:fs/promises' const src = await fs. readFile (process. argv [ 2 ] ?? 'input.pdf' ) const pdf = await PDFDocument . load (src) const font = await pdf. embedFont ( StandardFonts . HelveticaBold ) for ( const page of pdf. getPages ()) { const { width, height } = page. getSize () page. drawText ( 'CONFIDENTIAL' , { x : width / 2 - 140 , y : height / 2 , size : 64 , font, color : rgb ( 0.9 , 0.1 , 0.1 ), opacity : 0.25 , rotate : degrees (- 30 ), }) } const out = await pdf. save () await fs. writeFile ( 'watermarked.pdf' , out) console . log ( `watermarked ${pdf.getPageCount()} pages` ) 2.3 Demo: Merge PDFs ( pdf-lib ) import { PDFDocument } from 'pdf-lib' import fs from 'node:fs/promises' const merged = await PDFDocument . create () for ( const p of [ 'a.pdf' , 'b.pdf' , 'c.pdf' ]) { const src = await PDFDocument . load ( await fs. readFile (p)) const pages = await merged. copyPages (src, src. getPageIndices ()) pages. forEach ( pg => merged. addPage (pg)) } await fs. writeFile ( 'merged.pdf' , await merged. save ()) console . log ( `merged → ${merged.getPageCount()} pages` ) 2.4 Demo: Fill an AcroForm (run PdfInspect(form-fields) first to get checkedValue ) import { PDFDocument } from 'pdf-lib' import fs from 'node:fs/promises' const pdf = await PDFDocument . load ( await fs. readFile ( 'form.pdf' )) const form = pdf. getForm () form. getTextField ( 'full_name' ). setText ( 'John Smith' ) form. getCheckBox ( 'agree' ). check () // use setValue('Y') if PdfInspect gives checkedValue='Y' form. getRadioGroup ( 'gender' ). select ( 'M' ) // form.flatten() // call this to lock the form await fs. writeFile ( 'filled.pdf' , await pdf. save ()) console . log ( 'form filled' ) 2.5 Demo: Decrypt / rotate / extract pages // Decrypt import { PDFDocument } from 'pdf-lib' const pdf = await PDFDocument . load (buf, { password : 'secret' , ignoreEncryption : false }) await fs. writeFile ( 'unlocked.pdf' , await pdf. save ()) // Rotate page 1 by 90° pdf. getPage ( 0 ). setRotation ( degrees ( 90 )) // Extract pages 3 and 5 into a new PDF const out = await PDFDocument . create () const [p3, p5] = await out. copyPages (pdf, [ 2 , 4 ]) out. addPage (p3); out. addPage (p5) 3. OCR (scanned PDFs) PdfInspect(summary) // textType == 'scanned' PdfInspect(render, pageRange) // yields [<asset>/render-p1.png, ...] CloudImageUnderstand(image=<each png>, question='Extract all text accurately') 4. Format Conversion DocConvert(from="pdf", to="docx", sourcePath="…") # PDF → Word for editing DocConvert(from="docx", to="pdf", sourcePath="…") # Word → PDF for distribution DocConvert is faster and better at preserving layout than JsSandbox + pdf-lib ; prefer it for format conversion . 5. Common Error Fallbacks Symptom Cause Fix Garbled / square characters with pdfkit Default font has no CJK glyphs Call registerFont('cn', '/path/to/NotoSansCJK.ttf') first pdf-lib throws EncryptedPDFError on load File is encrypted PDFDocument.load(buf, { password: '…' }) Watermark uneven across pages Pages have different sizes Loop page.getSize() and compute x/y per page Merged PDF has font rendering differences Source PDFs have incomplete embedded fonts Rewrite with pdf-lib 's useObjectStreams: false TypeError: Cannot read properties of undefined (reading 'save') pdfkit has no doc.save() / doc.restore() (those are Canvas 2D APIs) Switch colors / sizes directly via doc.fillColor() / doc.fontSize() — no save/restore stack needed. Finish the document with doc.pipe(fs.createWriteStream(...)); doc.end() To patch a script: JsSandbox(action="edit-and-run", scriptPath=<previous path>, edits=[{find,replace}]) — only pass the diff.